DEMOGRAPHIC TRANSITION

The human population has maintained relatively gradual growth throughout most of history by high, and nearly equal, rates of deaths and births. Since about 1800, however, this situation has changed dramatically, as most societies have undergone major declines in mortality, setting off high growth rates due to the imbalance between deaths and births. Some societies have eventually had fertility declines and emerged with a very gradual rate of growth as low levels of births matched low levels of mortality.

There are many versions of demographic transition theory (Mason 1997), but there is some consensus that each society has the potential to proceed sequentially through four general stages of variation in death and birth rates and population growth. Most societies in the world have passed through the first two stages, at different dates and speeds, and the contemporary world is primarily characterized by societies in the last two stages, although a few are still in the second stage.

• Stage 1, presumably characterizing most of human history, involves high and relatively equal birth and death rates and little resulting population growth.
• Stage 2 is characterized by a declining death rate, especially concentrated in the years of infancy and childhood. The fertility rate remains high, leading to at least moderate population growth.
• Stage 3 involves further declines in mortality, usually to low levels, and initial sustained declines in fertility. Population growth may become quite high, as levels of fertility and mortality increasingly diverge.
• Stage 4 is characterized by the achievement of low mortality and the rapid emergence of low fertility levels, usually near those of mortality. Population growth again becomes quite low or negligible.

While demographers argue about the details of demographic change in the past 200 years, clearcut declines in birth and death rates appeared on the European continent and in areas of overseas European settlement in the nineteenth century, especially in the last three decades. By 1900, life expectancies in "developed" societies such as the United States were probably in the mid-forties, having increased by a few years in the century (Preston and Haines 1991). By the end of the twentieth century, even more dramatic gains in mortality were evident, with life expectancies reaching into the mid- and high-seventies.

The European fertility transition of the late 1800s to the twentieth century involved a relatively continuous movement from average fertility levels of five or six children per couple to bare levels of replacement by the end of the 1930s. Fertility levels rose again after World War II, but then began another decline about 1960. Some countries now have levels of fertility that are well below long-term replacement levels.

With a few exceptions such as Japan, most other parts of the developing world did not experience striking declines in mortality and fertility until the midpoint of the twentieth century. Gains in life expectancy became quite common and very rapid in the post-World War II period throughout the developing world (often taking less than twenty years), although the amount of change was quite variable. Suddenly in the 1960s, fertility transitions emerged in a small number of societies, especially in the Caribbean and Southeast Asia, to be followed in the last part of the twentieth century by many other countries.

Clear variations in mortality characterize many parts of the world at the end of the twentieth century. Nevertheless, life expectancies in countries throughout the world are generally greater than those found in the most developed societies in 1900. A much greater range in fertility than mortality characterizes much of the world, but fertility declines seem to be spreading, including in "laggard" regions such as sub-Saharan Africa.

The speed with which the mortality transition was achieved among contemporary lesser-developed countries has had a profound effect on the magnitude of the population growth that has occurred during the past few decades. Sweden, a model example of the nineteenth century European demographic transition, peaked at an annual rate of natural increase of 1.2 percent. In contrast, many developing countries have attained growth rates of over 3.0 percent. The world population grew at a rate of about 2 percent in the early 1970s but has now declined to about 1.4 percent, as fertility rates have become equal to the generally low mortality rates.

CAUSES OF MORTALITY TRANSITIONS

The European mortality transition was gradual, associated with modernization and raised standards of living. While some dispute exists among demographers, historians, and others concerning the relative contribution of various causes (McKeown 1976; Razzell 1974), the key factors probably included increased agricultural productivity and improvements in transportation infrastructure which enabled more efficient food distribution and, therefore, greater nutrition to ward off disease. The European mortality transition was also probably influenced by improvements in medical knowledge, especially in the twentieth century, and by improvements in sanitation and personal hygiene. Infectious and environmental diseases especially have declined in importance relative to cancers and cardiovascular problems. Children and infants, most susceptible to infectious and environmental diseases, have showed the greatest gains in life expectancy.

The more recent and rapid mortality transitions in the rest of the world have mirrored the European change with a movement from infectious/environmental causes to cancers and cardiovascular problems. In addition, the greatest beneficiaries have been children and infants. These transitions result from many of the same factors as the European case, generally associated with economic development, but as Preston (1975) outlines, they have also been influenced by recent advances in medical technology and public health measures that have been imported from the highly-developed societies. For instance, relatively inexpensive vaccines are now available throughout the world for immunization against many infectious diseases. In addition, airborne sprays have been distributed at low cost to combat widespread diseases such as malaria. Even relatively weak national governments have instituted major improvements in health conditions, although often only with the help of international agencies.

Nevertheless, mortality levels are still higher than those in many rich societies due to such factors as inadequate diets and living conditions, and inadequate development of health facilities such as hospitals and clinics. Preston (1976) observes that among non-Western lesser-developed countries, mortality from diarrheal diseases (e.g., cholera) has persisted despite control over other forms of infectious disease due to the close relationship between diarrheal diseases, poverty, and ignorance—and therefore a nation's level of socioeconomic development.

Scholars (Caldwell 1986; Palloni 1981) have warned that prospects for future success against high mortality may be tightly tied to aspects of social organization that are independent of simple measures of economic well-being: Governments may be more or less responsive to popular need for improved health; school system development may be important for educating citizens on how to care for themselves and their families; the equitable treatment of women may enhance life expectancy for the total population.

Recent worldwide mortality trends may be charted with the help of data on life expectancy at age zero that have been gathered, sometimes on the basis of estimates, by the Population Reference Bureau (PRB), a highly respected chronicler of world vital rates. For 165 countries with relatively stable borders over time, it is possible to relate estimated life expectancy in 1986 with the same figure for 1998. Of these countries, only 13.3 percent showed a decline in life expectancy during the time period. Some 80.0 percent had overall increasing life expectancy, but the gains were highly variable. Of all the countries, 29.7 percent actually had gains of at least five years or more, a sizable change given historical patterns of mortality.

An indication of the nature of change may be discerned by looking at Figure 1, which shows a graph of the life expectancy values for the 165 countries with stable borders. Each point represents a country and shows the level of life expectancy in 1986 and in 1998. Note the relatively high levels of life expectancy by historical standards for most countries in both years. Not surprisingly, there is a strong tendency for life expectancy values to be correlated over time. A regression straight line, indicating average life expectancy in 1998 as a function of life expectancy in 1986 describes this relationship. As suggested above, the levels of life expectancy in 1998 tend to be slightly higher than the life expectancy in 1986. Since geography is highly associated with economic development, the points on the graph generally form a continuum from low to high life expectancy. African countries tend to have the lowest life expectancies, followed by Asia, Oceania, and the Americas. Europe has the highest life expectancies.

The African countries comprise virtually all the countries with declining life expectancies, probably a consequence of their struggles with acquired immune deficiency syndrome (AIDS), malnutrition, and civil disorder. Many of them have lost several years of life expectancy in a very short period of time. However, a number of the African countries also have sizeable increases in life expectancies.

Asian and American countries dominate the mid-levels of life expectancy, with the Asian countries showing a strong tendency to increase their life expectancies, consistent with high rates of economic development.

Unfortunately, Figure 1 does not include the republics of the former Soviet Union, since exactly comparable data are not available for both time points. Nevertheless, there is some consensus among experts that life expectancy has deteriorated in countries such as Russia that have made the transition from communism to economically-unstable capitalism.

WHAT DRIVES FERTILITY RATES?

The analysis of fertility decline is somewhat more complicated analytically than mortality decline. One may presume that societies will try, if given resources and a choice, to minimize mortality levels, but it seems less necessarily so that societies have an inherent orientation toward low fertility, or, for that matter, any specific fertility level. In addition, fertility rates may vary quite widely across societies due to factors (Bongaarts 1975) that have little relationship to conscious desires such as prolonged breastfeeding which supresses reproductive ovulation in women, the effectiveness of birth control methods, and the amount of involuntary foetal abortion. As a result of these analytic ambiguities, scholars seem to have less consensus on the social factors that might produce fertility than mortality decline (Hirschman 1994; Mason 1997).

Coale (1973), in an attempt to reconcile the diversity of circumstances under which fertility declines have been observed to occur, identified three major conditions for a major fall in fertility:

1. Fertility must be within the calculus of conscious choice. Parents must consider it an acceptable mode of thought and form of behavior to balance the advantages and disadvantages of having another child.
2. Reduced fertility must be viewed as socially or economically advantageous to couples.
3. Effective techniques of birth control must be available. Sexual partners must know these techniques and have a sustained will to use the them.

Beyond Coale's conditions, little consensus has emerged on the causes of fertility decline. There are, however, a number of major ideas about what causes fertility transitions that may be summarized in a few major hypotheses.

A major factor in causing fertility change may be the mortality transition itself. High-mortality societies depend on high fertility to ensure their survival. In such circumstances, individual couples will maximize their fertility to guarantee that at least a few of their children survive to adulthood, to perpetuate the family lineage and to care for them in old age. The decline in mortality may also have other consequences for fertility rates. As mortality declines, couples may perceive that they can control the survival of family members by changing health and living practices such as cleanliness and diet. This sense of control may extend itself to the realm of fertility decisions, so that couples decide to calculate consciously the number of children they would prefer and then take steps to achieve that goal.

Another major factor may be the costs and benefits of children. High-mortality societies are often characterized by low technology in producing goods; in such a situation (as exemplified by many agricultural and mining societies), children may be economically useful to perform low-skilled work tasks. Parents have an incentive to bear children, or, at the minimum, they have little incentive not to bear children. However, high-technology societies place a greater premium on highly-skilled labor and often require extended periods of education. Children will have few economic benefits and may become quite costly as they are educated and fed for long periods of time.

Another major factor that may foster fertility decline is the transfer of functions from the family unit to the state. In low-technology societies, the family or kin group is often the fundamental unit, providing support for its members in times of economic distress and unemployment and for older members who can no longer contribute to the group through work activities. Children may be viewed as potential contributors to the unit, either in their youth or adulthood. In high-technology societies, some of the family functions are transferred to the state through unemployment insurance, welfare programs, and old age retirement systems. The family functions much more as a social or emotional unit where the economic benefits of membership are less tangible, thus decreasing the incentive to bear children.

Other major factors (Hirschman 1994; Mason 1997) in fertility declines may include urbanization and gender roles. Housing space is usually costly in cities, and the large family becomes untenable. In many high-technology societies, women develop alternatives to childbearing through employment outside their homes, and increasingly assert their social and political rights to participate equally with men in the larger society. Because of socialization, men are generally unwilling to assume substantial child-raising responsibilities, leaving partners with little incentive to participate in sustained childbearing through their young adult lives.

No consensus exists on how to order these theories in relative importance. Indeed, each theory may have more explanatory power in some circumstances than others, and their relative importance may vary over time. For instance, declines in mortality may be crucial in starting fertility transitions, but significant alterations in the roles of children may be key for completing them. Even though it is difficult to pick the "best" theory, every country that has had a sustained mortality decline of at least thirty years has also had some evidence of a fertility decline. Many countries seem to have the fertility decline precondition of high life expectancy, but fewer have achieved the possible preconditions of high proportions of the population achieving a secondary education.

EUROPEAN FERTILITY TRANSITION

Much of what is known about the process of fertility transition is based upon research at Princeton University (known as the European Fertility Project) on the European fertility transition that took place primarily during the seventy-year period between 1870 and 1940. Researchers used aggregate government-collected data for the numerous "provinces" or districts of countries, typically comparing birth rates across time and provinces.

In that almost all births in nineteenth-century Europe occurred within marriage, the European model of fertility transition was defined to take place at the point marital fertility was observed to fall by more than 10 percent (Coale and Treadway 1986). Just as important, the Project scholars identified the existence of varying levels of natural fertility (birth rates when no deliberate fertility control is practiced) across Europe and throughout European history (Knodel 1977). Comparative use of natural fertility models and measures derived from these models have been of enormous use to demographers in identifying the initiation and progress of fertility transitions in more contemporary contexts.

Most scholars have concluded that European countries seemed to start fertility transitions from very different levels of natural fertility but moved at quite similar speeds to similar levels of controlled fertility on the eve of World War II (Coale and Treadway 1986). As the transition progressed, areal differences in fertility within and across countries declined, while the remaining differences were heavily between countries (Watkins 1991).

Although some consensus has emerged on descriptive aspects of the fertility transition, much less agreement exists on the social and economic factors that caused the long-term declines. Early theorists of fertility transitions (Notestein 1953) had posited a simple model driven by urban-industrial social structure, but this perspective clearly proved inadequate. For instance, the earliest declines did not occur in England, the most urban-industrial country of the time, but were in France, which maintained a strong rural culture. The similarity of the decline across provinces and countries of quite different social structures also seemed puzzling within the context of previous theorizing. Certainly, no one has demonstrated that variations in the fertility decline across countries, either in the timing or the speed, were related clearly to variations in crude levels of infant mortality, literacy rates, urbanization, and industrialization. Other findings from recent analysis of the European experience include the observation that in some instances, reductions in fertility preceded reductions in mortality (Cleland and Wilson 1987), a finding that is inconsistent with the four-stage theory of demographic transition.

The findings of the European Fertility Project have led some demographers (Knodel and van de Walle 1979) to reformulate ideas about why fertility declined. They suggest that European couples were interested in a small family well before the actual transition occurred. The transition itself was especially facilitated by the development of effective and cheap birth control devices such as the condom and diaphragm. Information about birth control rapidly and widely diffused through European society, producing transitions that seemed to occur independently of social structural factors such as mortality, urbanization, and educational attainment. In addition, these scholars argue that "cultural" factors were also important in the decline. This is based on the finding that provinces of some countries such as Belgium differed in their fertility declines on the basis of areal religious composition (Lesthaeghe 1977) and that, in other countries such as Italy, areal variations in the nature of fertility decline were related to political factors such as the Socialist vote, probably reflecting anticlericalism (Livi-Bacci 1977). Others (Lesthaeghe 1983) have also argued for "cultural" causes of fertility transitions.

While the social causes of the European fertility transition may be more complex than originally thought, it may still be possible to rescue some of the traditional ideas. For instance, mortality data in Europe at the time of the fertility transition were often quite incomplete or unreliable, and most of the studies focused on infant (first year of life) mortality as possible causes of fertility decline. Matthiessen and McCann (1978) show that mortality data problems make some of the conclusions suspect and that infant mortality may sometimes be a weak indicator of child survivorship to adulthood. They argue that European countries with the earliest fertility declines may have been characterized by more impressive declines in post-infant (but childhood) mortality than infant mortality.

Conclusions about the effects of children's roles on fertility decline have often been based on rates of simple literacy as an indicator of educational system development. However, basic literacy was achieved in many European societies well before the major fertility transitions, and the major costs of children would occur when secondary education was implemented on a large scale basis, which did not happen until near the end of the nineteenth century (Van de Walle 1980). In a time-series analysis of the United States fertility decline from 1870 to the early 1900s, Guest and Tolnay (1983) find a nearly perfect tendency for the fertility rate to fall as the educational system expanded in terms of student enrollments and length of the school year. Related research also shows that educational system development often occurred somewhat independently of urbanization and industrialization in parts of the United States (Guest 1981).

An important methodological issue in the study of the European transition (as in other transitions) is how one models the relationship between social structure and fertility. Many of the research reports from the European Fertility Project seem to assume that social structure and fertility had to be closely related at all time points to support various theories about the causal importance of such factors as mortality and children's roles, but certain lags and superficial inconsistencies do not seem to prove fundamentally that fertility failed to respond as some of the above theories would suggest. The more basic question may be whether fertility eventually responded to changes in social structure such as mortality.

Even after admitting some problems with previous traditional interpretations of the European fertility transition, one cannot ignore the fact that the great decline in fertility occurred at almost the same time as the great decline in mortality and was associated (even if loosely) with a massive process of urbanization, industrialization, and the expansion of educational systems.

FERTILITY TRANSITIONS IN THE DEVELOPING WORLD

The great majority of countries in the developing world have undergone some fertility declines in the second half of the twentieth century. While the spectacularly rapid declines (Taiwan, South Korea) receive the most attention, a number are also very gradual (e.g. Guatemala, Haiti, Iraq, Cambodia), and a number are so incipient (especially in Africa) that their nature is difficult to discern.

The late twentieth century round of fertility transitions has occurred in a very different social context than the historical European pattern. In the past few decades, mortality has declined very rapidly. National governments have become very attuned to checking their unprecedented national growth rates through fertility control. Birth control technology has changed greatly through the development of inexpensive methods such as the intrauterine device (IUD). The world has become more economically and socially integrated through the expansion of transportation and developments in electronic communications, and "Western" products and cultural ideas have rapidly diffused throughout the world. Clearly, societies are not autonomous units that respond demographically as isolated social structures.

Leaders among developing countries in the process of demographic transition were found in East Asia and Latin America, and the Carribbean (Coale 1983). The clear leaders among Asian nations, such as South Korea and Taiwan, generally had experienced substantial economic growth, rapid mortality decline, rising educational levels, and exposure to Western cultural influences (Freedman 1998). By 1998, South Korea and Taiwan had fertility rates that were below long-term replacement levels. China also experienced rapidly declining fertility, which cannot be said to have causes in either Westernization or more than moderate economic development, with a life expectancy estimated at seventy-one years and a rate of natural increase of 1.0 percent (PRB 1998).

Major Latin American nations that achieved substantial drops in fertility (exceeding 20 percent) in recent decades with life expectancies surpassing sixty years include Argentina, Brazil, Chile, Columbia, the Dominican Republic, Jamaica, Mexico, and Venezuela. All of these have also experienced substantial changes in mortality, education, or both, and economic development.

Unlike the European historical experience, fertility declines in the post-1960 period have not always sustained themselves until they reached near replacement levels. A number of countries have started declines but then leveled off with three or four children per reproductive age woman. For instance, Malaysia was considered a "miracle" case of fertility decline, along with South Korea and Taiwan, but in recent years its fertility level has stabilized somewhat above the replacement level.

Using the PRB data for 1986 and 1998, we can trace recent changes for 166 countries in estimated fertility as measured by the Total Fertility Rate (TFR), an indicator of the number of children typically born to a woman during her lifetime. Some 80.1 percent of the countries showed declines in fertility. Of all the countries, 37.3 percent had a decline of at least one child per woman, and 9.0 percent had a decline of at least two children per woman.

The region that encompasses countries having the highest rates of population growth is sub-Saharan Africa. Growth rates generally exceed 2 percent, with several countries having rates that clearly exceed 3 percent. This part of the world has been one of the latest to initiate fertility declines, but in the 1986–1998 period, Botswana, Kenya, and Zimbabwe all sustained fertility declines of at least two children per woman, and some neighboring societies were also engaged in fertility transition. At the same time, many sub-Saharan countries are pre-transitional or only in the very early stages of a transition. Of the twenty-five countries that showed fertility increases in the PRB data, thirteen of them were sub-Saharan nations with TFRs of at least 5.0.

In general, countries of the Middle East and regions of Northern Africa populated by Moslems have also been slow to embark on the process of fertility transition. Some (Caldwell 1976) found this surprising since a number had experienced substantial economic advances and invited the benefits of Western medical technology in terms of mortality reduction. Their resistance to fertility transitions had been attributed partly to an alleged Moslem emphasis on the subordinate role of women to men, leading them to have limited alternatives to a homemaker role. However, the PRB data for 1986–1998 indicate that some of these countries (Algeria, Bangladesh, Jordan, Kuwait, Morocco, Syria, Turkey) are among the small number that achieved reduction of at least two children per woman.

The importance of the mortality transition in influencing the fertility transition is suggested by Figure 2. Each dot is a country, positioned in terms of graphical relationship in the PRB data between life expectancy in 1986 and the TFR in 1998. The relationship is quite striking. No country with a life expectancy less than fifty has a TFR below 3.0. Remember that before the twentieth century, virtually all countries had life expectancies below fifty years. In addition, the figure shows a very strong tendency for countries with life expectancies above seventy to have TFRs below 2.0.

For a number of years, experts on population policy were divided on the potential role of contraceptive programs in facilitating fertility declines (Davis 1967). Since contraceptive technology has become increasingly cheap and effective, some (Enke 1967) argue that modest international expenditures on these programs in high-fertility countries could have significant rapid impacts on reproduction rates. Others (Davis 1967) point out, however, that family planning programs would only permit couples to achieve their desires, which may not be compatible with societal replacement level fertility. The primary implication was that family planning programs would not be effective without social structures that encouraged the small family. A recent consensus on the value of family planning programs relative to social structural change seems to have emerged. Namely, family planning programs may be quite useful for achieving low fertility where the social structure is consistent with a small family ideal (Mauldin and Berelson 1978).

While the outlook for further fertility declines in the world is good, it is difficult to say whether and when replacement-level fertility will be achieved. Many, many major social changes have occurred in societies throughout the world in the past half-century. These changes have generally been unprecented in world history, and thus we have little historical experience from which to judge their impact on fertility, both levels and speed of change (Mason 1997).

Some caution should be excercised about future fertility declines in some of the societies that have been viewed as leaders in the developing world. For instance, in a number of Asian societies, a strong preference toward sons still exists, and couples are concerned as much about having an adequate number of sons survive to adulthood as they are about total sons and daughters. Since pre-birth gender control is still difficult, many couples have a number of girl babies before they are successful in bearing a son. If effective gender control is achieved, some of these societies will almost certainly attain replacement-level fertility.

In other parts of the world such as sub-Saharan Africa, the future of still-fragile fertility transitions may well depend on unknown changes in the organization of families. Caldwell (1976), in a widely respected theory of demographic transition that incorporates elements of both cultural innovation and recognition of the role of children in traditional societies in maintaining net flows of wealth to parents, has speculated that the traditional extended kinship family model now predominant in the region facilitates high fertility. Families often form economic units where children are important work resources. The extended structure of the household makes the cost of any additional member low relative to a nuclear family structure. Further declines in fertility will depend on the degree to which populations adopt the "Western" nuclear family, either through cultural diffusion or through autonomous changes in local social structure.

Taking the long view, the outlook for a completed state of demographic transition for the world population as a whole generally appears positive if not inevitable, although demographers are deeply divided on estimates of the size of world population at equilibrium, the timing of completed transition, the principal mechanisms at work, and the long-term ecological consequences. Certainly, the world population will continue to grow for some period of time, if only as a consequence of the previous momentum of high fertility relative to mortality. Most if not all demographers, however, subscribe to the view expressed by Coale (1974, p. 51) that the entire process of global demographic transition and the phase of phenomenal population growth that has accompanied it will be a transitory (albeit spectacular) episode in human population history.

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Avery M. Guest Gunnar Almgren

DEMOGRAPHIC TRANSITION

The term demographic transition refers to the decline in mortality and fertility from the high rates characteristic of premodern and low-income societies to the low rates characteristic of modern and high-income societies. Demographic transition is a central concept in demography, and there is a large literature examining the nature and the causes of the phenomenon. On the face of it, demographic transition is simply a description of a pattern of historical trends in vital rates. The influential discussions of demographic transition, however, interweave description with explanation of mortality and fertility declines, and this has made it difficult to separate the descriptive concept from the far more controversial "theory" of demographic transition.

History of the Concept

Although the term demographic transition originated with Frank W. Notestein in the mid-twentieth century, the first systematic effort to describe distinctive demographic regimes that represented historical stages linked to broader societal changes is credited to the work of the French demographer Adolphe Landry dating back to the first decade of the twentieth century. In Landry's formulation, elaborated in greater detail in a book published in 1934, demographic regimes are a function of the material aspirations of individuals and the productive potential of the economic system. In the "primitive" regime characteristic of subsistence economies, mortality but not fertility is constrained by economic factors, and population size tends to the maximum that economic resources can support. In the "intermediate" regime, in an effort to preserve family wealth, fertility is depressed by late marriage and celibacy, and population size falls below the maximum that the economy can support. The "modern" regime emerges when economic productivity reaches high levels and individuals have well-formulated aspirations for a high standard of living. To facilitate the achievement of those material aspirations, fertility becomes an object of conscious limitation, chiefly through various techniques of birth control but also through late marriage and celibacy. Population size is far smaller than the economy could support were individuals willing to accept lower standards of living–indeed negative population growth rates are a distinct possibility.

An alternative three-stage formulation of demographic transition was offered by the American demographer Warren Thompson in 1929. Thompson classified the countries of the world into three groups: (1) countries with high birth rates and high but declining death rates, facing the prospect of rapid population growth; (2) countries with declining birth and death rates in certain socioeconomic strata, with the rate of decline in death rates outstripping the rate of decline in birthrates; and (3) countries with rapidly declining birth and death rates, with fertility declining more rapidly than mortality, resulting in a declining population growth rate. Thompson assumed that these three groups were representative of historical stages. But by limiting his purview to contemporary demographic regimes, Thompson offered a truncated evolutionary scheme–he described neither a full-fledged pre-transition regime nor a post-transition regime. In addition, Thompson had less to say about the causes of demographic change than his predecessor Landry and his successors Notestein and Kingsley Davis.

Notestein's formulation has probably been the most influential, appearing just at the onset of a five-decade period of widespread concern about the development-retarding effects of rapid population growth in Africa, Asia, and Latin America. Notestein held that the lessons he had distilled from the European historical experience were applicable to other regions and could inform public policies. Like Thompson, Notestein focused on the societal variation he observed at the time and therefore devoted limited attention to pretransitional regimes. He was aware that mortality decline was well underway in Africa, Asia, and Latin America yet fertility was essentially unchanged; these societies with high-population-growth potential constituted his first type of demographic regime. A second were those countries where fertility decline was well established but incomplete (Japan, the Soviet Union, and the southern cone of South America), and the third type were the low mortality and fertility populations of Europe, North America, and Australia. What gave Notestein's piece special power was his succinct yet compelling explanation for the declines in mortality and fertility (discussed below). One crucial element in Notestein's argument was that mortality is likely to respond more quickly than fertility to the forces of change, and therefore it is all but inevitable that societies experience a transitional period during which birth rates exceed death rates by a substantial margin, generating rapid population growth.

The Demography of Demographic Transition

Since the 1950s the standard formulation of demographic transition comprises three stages: pretransition regimes, characterized by high (and fluctuating) mortality and high fertility; transitional regimes, characterized by declining mortality and declining fertility, with mortality decline typically running ahead of fertility decline, resulting in population growth; and posttransitional regimes, with low mortality and low (and possibly fluctuating) fertility. The pretransition and posttransition regimes are assumed to be essentially in long-term equilibrium, with transitional regimes acting as a bridge between the two. In pretransition regimes, life expectancy at birth is less than 40 years and women bear on average between five and eight births over their reproductive lifespan, whereas in posttransition regimes, life expectancy at birth exceeds 65 years and women bear on average 2.5 or fewer births.

As empirical studies have accumulated, it has become apparent that pretransition and posttransition regimes are far from uniform in their vital rates. In general, pretransition mortality was lower in Europe than in Africa and Asia–life expectancy closer to 40 years in the former and 30 years in the latter. Even within Europe there was great variability in mortality rates, with the percentage of children dying in infancy ranging from over 30 percent in parts of Bavaria to 10 percent in southern England at the onset of demographic transition. Mortality was also characterized by substantial variation over time, reflecting nutritional adversity and epidemics of infectious disease. Nonmarriage and late marriage significantly reduced fertility rates in pretransition Europe, whereas marriage of women was close to universal in most African and Asian societies and generally occurred soon after menarche (the first menstrual period). As a result, in African and Asian societies fertility levels were higher, even though postpartum sexual abstinence and extended breast-feeding had a moderating effect on fertility rates. There is evidence, still subject to some dispute, that deliberate and conscious regulation of childbearing–the spacing of births–and perhaps of family size as well was common in pretransition African and Asian societies. Fertility within marriage appears to have been subject to far less control in pretransition Europe, although withdrawal was a widely known method of contraception that later was extensively practiced to control fertility in many parts of Europe.

Posttransition populations also show considerable variability in their demographic rates. Continuing declines in mortality at older ages have led to life expectancies at birth approaching 80 years in some European, North American, and East Asian countries, whereas life expectancy has slid below 70 years in eastern Europe because of deteriorating health conditions. The AIDS pandemic, affecting transitional societies especially in eastern and southern Africa, is further demonstration that improvements in health are not necessarily permanent, indeed that reductions in life expectancy on the order of 15 to 20 years can occur over a period as short as two decades. Such nonuniform trends in mortality in transitional and posttransition populations were not fore-seen in the original formulations of the demographic transition. Furthermore, fertility in posttransition countries has in general failed to settle on the replacement level of an average of just over two births per woman over the reproductive lifespan. For decades, births per woman remained substantially above that level, ranging between 2.5 and 3 in the southern cone of South America (Argentina, Chile, and Uruguay) in what seemed a relatively stable posttransition regime. In contrast, in the decades since 1970, fertility has fallen below replacement in most European countries, and even below 1.5 births per woman in some countries of southern and eastern Europe.

The combinations of death rates and birth rates observed in pretransition and posttransition populations allow for modest demographic growth and decline, although over long stretches of time growth rates in pretransition societies were close to zero (typically less than 0.5 percent per year). The rate of population growth in pretransition and posttransition societies is dwarfed by the rate of growth in transitional societies–a result of the time lag between the mortality and fertility declines during the process of transition and, additionally but not universally, a temporary fertility increase early in the transitional stage. Such temporary fertility increases are in all likelihood a physiological response to improved maternal and child health and changes in postpartum practices. The "transition multiplier"–the ratio of the posttransition population size to the pretransition population size–is determined by the extent to which birth rates exceed death rates and the length of time during which that condition prevails. Transition multipliers are high when fertility decline begins from a high initial level and occurs substantially later than mortality decline and proceeds slowly.

An important aspect of the dynamics of transition is that population growth does not immediately subside once fertility falls to replacement level. The high fertility and low childhood mortality of the transitional demographic regime further accentuates the young age-structure that characterizes pretransition populations. This means that for several decades relatively large cohorts pass through the childbearing years. The additional population growth that occurs while the age-structure shifts to its post-transition shape is called population momentum. Population momentum is a substantial component of population growth over the course of demographic transition, typically contributing 30 to 40 percent of the total growth. Formal demographic analysis and simulation exercises demonstrate that population momentum is inversely related to the level of posttransition fertility and to the pace of fertility decline.

The demographic transitions in European populations differed substantially from the transitions in non-European populations in the magnitude of the rate of transitional population growth. In Europe, where the decline in fertility followed close on the heels of the decline in mortality, both starting from relatively low pretransition levels, the rate of natural increase (birth rates minus death rates) during the transitional period from 1800 to 1950 ranged between 0.5 and 1 percent per year, and the transition multiplier was roughly four (a ratio moderated somewhat by overseas emigration). In most non-European populations, mortality declines began during the first decades of the twentieth century and became steep in the decades after World War II, whereas fertility declines (from relatively high initial levels) began in earnest only after 1960 or later. As a result, many non-European countries experienced population growth rates of 2 to 3.5 percent per year for four decades or longer, and the transition multipliers (calculated using projected population numbers) range from 8 to 20. The highest multipliers are found in those countries with slow fertility declines, for example the Philippines, where the pretransition population size was about 8 million, the 2002 population was 79 million, and the posttransition population size is projected to be as high as 150 million, according to the United Nations, and Guatemala (pretransition population of 1.4 million, 2002 population of 12 million, and posttransition population projected as high as 30 million). In no European country did demographic transition produce population growth on this proportionate scale. Population multipliers of this magnitude, often combined with a pretransition population size that was large in absolute terms, are bound to have many and varied repercussions for social, economic, political, and cultural systems–some positive but no doubt also some deleterious.

Explanations for Demographic Transition

The many efforts, from Landry to the present, seeking to identify the forces generating demographic transition fall into two major sets. One regards fertility decline as an inevitable response to the population growth induced by mortality decline, which is therefore all that requires explanation. The second views fertility decline as a response to a richer and more diverse set of social, economic, political, and cultural forces.

While mortality decline has presented less of an explanatory challenge than fertility decline, there has been ample debate about its causes. Economic transformations that improved standards of living–food, clothing, sanitation, housing–appears to account for much of the decline of mortality in Europe. Samuel Preston argued in 1975, however, that economic change, as captured by growth in income per capita, accounts for only a small fraction of mortality decline in non-European populations in the twentieth century. Political stability and the emergence of effective nation-states complement the effects of economic change by leading to more reliable access to food and improved public sanitation. New medical technologies made a minor contribution to the decline of mortality in Europe in the eighteenth and nineteenth centuries but were a major factor in the sharp reduction in mortality from infectious diseases in the developing countries in the twentieth century. A final factor is improved personal hygiene (hand washing, preparation of food, and so forth), with new habits adopted in response to formal school instruction, public-health education campaigns, and word-of-mouth information.

Some scholars have argued that mortality decline is a sufficient cause of fertility decline and hence accounts for the demographic transitions of the past two centuries. Strictly speaking, the explanatory factor is not mortality decline but population growth. In 1963 Davis described household-level strain created by significantly larger younger generations vying for valued economic and social resources. Successively larger cohorts (in particular, the increase in the ratio of sons to fathers) disrupt the equilibrium of the traditional family. Other scholars have noted that mortality decline, normally accompanied by improved health of the population, should increase economic productivity and through that channel exercise a positive indirect effect on fertility. Finally, mortality decline encourages a change in personal psychologies away from fatalism toward a greater sense of self-control over one's destiny, and this facilitates the exercise of deliberate fertility regulation.

Fertility declines have occurred under widely varying social and economic circumstances but virtually never in the absence of mortality decline, and this can be taken as strong evidence that mortality decline is the primary cause of fertility decline. Theories of demographic homeostasis posit that human societies gravitate toward demographic regimes with growth rates near zero; multiple and diverse societal institutions act as governors on population growth and enforce the tendency to oscillate near zero growth. Marked departures meet with the appropriate demographic response–increases in fertility to make up for mortality crises, decreases in fertility in response to mortality decline, or migration that offsets increases or decreases in rates of natural increase (a key element in Davis's theory of "multiphasic response"). While appealing as a general theory of population dynamics, homeostatic theory is not very informative about the demographic transitions that occurred during the nineteenth and twentieth centuries. The end results of these transitions, as noted earlier, were multifold increases in population size. It is not clear how homeostatic theory accommodates this failure of fertility or migration to compensate for the impact of mortality declines. Moreover, the diversity of the pretransition equilibrium levels of fertility and mortality and of the lags between mortality and fertility declines, as reflected in the large variation in transition multipliers, is a major empirical fact that demands explanation. Surely the explanation lies in the conditioning influence of social, economic, and cultural forces.

In the second set of explanations for fertility decline, mortality decline is not the sole causal agent. Indeed, Notestein, in his seminal 1945 work, hardly mentioned mortality decline as a motivation for fertility decline. Instead he argued that both mortality and fertility decline in response to urbanization and changes in the economy (which changed the costs and benefits of children and led to rising standards of living and increased material aspirations) and to growth in individualism and secularism. Notestein's argument has been elaborated in a large subsequent literature on the causes of fertility decline that has featured economic forces, cultural changes, and changes in birth control costs.

Economic theories of fertility decline focus on the causal impact of changes in the costs and benefits of children and childrearing. The fundamental cause of fertility decline is the (perceived) decreasing affordability of large numbers of children. Demographers have resisted giving pride of place to microeconomic changes in models of fertility decline, perhaps because of disciplinary biases but more importantly because of weak empirical associations between macroeconomic changes and fertility decline. The Princeton European Fertility Project, for example, uncovered no systematic relationship at the provincial level between the onset of fertility decline and socioeconomic variables such as levels of urbanization and nonagricultural employment. But other empirical research that has had access to a larger number of economic variables that provide a more complete portrait of the economic system, as well as studies conducted at lower levels of aggregation (the local community or the household), attribute much greater causal impact to economic change. This includes studies on fertility declines in England, Italy, Bavaria, and Prussia. Moreover, it seems likely that cognitive dimensions–in particular, economic aspirations and expectations–mediate the relationship between economic change and fertility. The causal force may not be economic circumstances per se but rather the relationship between economic aspirations and expectations (that is, what individuals want as opposed to what they expect). This can explain why fertility declines have occurred in the presence of both improving and deteriorating economic conditions.

Mortality decline and economic change are the core elements of a model for fertility decline. High fertility is compatible neither with low mortality nor with high-income, modern economies. Both mortality regimes and economic systems have been transformed during the past two centuries, to an extent and at a rate that are extraordinary by any measure. If one wishes to go back further in the causal chain and ask why this has occurred, inevitably one is led to the scientific and technological revolutions of the past four centuries. Ultimately it is these revolutions that lengthened life expectancy and made bearing large numbers of children inconsistent with modernity.

Another stream in the literature on the causes of fertility decline emphasizes the determining role of attitudes about and values related to family life. Ron Lesthaeghe has proposed that the decline of fertility in Europe was caused by the synergistic effects of economic changes and changes in the moral and ethical domain. Lesthaeghe stresses the emergence of secularism, materialism, individualism, and self-fulfillment as dominant values that in combination undermine the satisfactions derived from having children. John C. Caldwell argued in 1982 that a shift in the morality governing family life–in particular, a higher valuation of the conjugal relationship and of investments in children–leads to a dismantling of high-fertility reproductive regimes. Fertility decline is triggered by emotional nucleation of the family, itself a response to broader economic and cultural changes. For both scholars, the critical cultural change has less to do with the value of children narrowly defined and more to do with the nature of intergenerational relations and the perceived contribution of childbearing to the achievement of a desired standard and style of living. But whether changing mentalities and moralities about family life are themselves a sufficient cause of sustained and substantial fertility decline is doubtful, absent the precondition of mortality decline. Certain cultural changes, of course, might provoke both mortality and fertility declines, for example an increase in the value placed on investments in children, per child.

A final cluster of determinants of the timing and pace of fertility decline can be gathered under the heading "costs of birth control." The argument is that various economic, social, psychic, and health factors can make birth control practices prohibitively costly, and hence the reduction or elimination of such costs is a prerequisite for fertility decline. Ansley Coale and Richard Easterlin both highlighted the potentially important causal role of the costs of birth control, and the empirical record now contains numerous studies that demonstrate that reduction in birth control costs can accelerate fertility decline. In the period since 1960, the most prominent strategy for reducing birth control costs has been the provision of contraceptives free of charge or at nominal price through public and private family planning programs. But limited access to contraception is by no means the only obstacle to use, and some scholars have argued that personal knowledge and social legitimacy of contraception are perhaps more critical than the mere provision of contraceptive technology.

Conclusion

The debate that began in the 1950s and is still continuing about the aims of population policy and the nature and scope of interventions can be viewed as a debate about how to weight the various determinants of demographic transition. If one follows Notestein's reading of the European historical experience, then the decisive factors are social and economic change, and the availability of contraceptive technology is of little importance. Davis as well leaves one less than sanguine about the likely contribution of programs that make family planning and reproductive health services more accessible and less expensive. Coale and Easterlin provide a stronger rationale for investment in such programs. Rapid population growth–a function of the gap between mortality and fertility declines–has been a primary public policy concern. But the demography of pre-transition and post-transition populations differ in many other respects–posttransition, the age-structure of the population is older, individuals' lives are far lengthier, and childrearing occupies a much smaller portion of those lives. These outcomes of demographic transition increasingly are the focus of public policy debates about population dynamics.

See also: Davis, Kingsley; Development, Population and; Epidemiological Transition; Fertility Transition, Socioeconomic Determinants of; Health Transition; Homeostasis; Landry, Adolphe; Notestein, Frank W.; Mortality Decline; Second Demographic Transition; Thompson, Warren S.

bibliography

Caldwell, John C. 1982. Theory of Fertility Decline. London: Academic Press.

Chesnais, Jean-Claude. 1992. The Demographic Transition. Oxford: Oxford University Press.

Cleland, John. 2001. "The Effects of Improved Survival on Fertility: A Reassessment." In Global Fertility Transition, Supplement to Volume 27of Population and Development Review, ed. Rodolfo A. Bulatao and John B. Casterline. New York: Population Council.

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Davis, Kingsley. 1963. "The Theory of Change and Response in Modern Demographic History." Population Index 29: 345–366.

Easterlin, Richard. 1975. "An Economic Framework for Fertility Analysis." Studies in Family Planning 6: 54–63.

Goldstein, Joshua. 2002. "Population Momentum for Gradual Demographic Transition." Demography 39: 65–74.

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Landry, Adolphe. 1934. La revolution démographique. Paris: Sirey.

Lloyd, Cynthia, and Serguey Ivanov. 1988. "The Effects of Improved Child Survival on Family Planning Practices and Fertility." Studies in Family Planning 19: 141–161.

Mason, Karen Oppenheim. 1997. "Explaining Fertility Transitions." Demography 34: 443–454.

Montgomery, Mark, and Barney Cohen, eds. 1998. From Death to Birth: Mortality Decline and Reproductive Change. Washington, D.C.: National Academy Press.

Notestein, Frank W. 1945. "Population: The Long View." In Food for the World, ed. Theodore W. Schultz. Chicago: University of Chicago Press.

Preston, Samuel. 1975. "The Changing Relation between Mortality and Level of Economic Development." Population Studies 29: 231–248.

Wilson, Chris, and Pauline Airey. 1999. "How Can a Homeostatic Perspective Enhance Demographic Transition Theory?" Population Studies 53: 117–128.

John B. Casterline

Demographic Transition

HISTORY OF THE THEORY

BIBLIOGRAPHY

The term demographic transition originally described the major social shift that occurred in Western societies from the late nineteenth century to the 1930s. At that time, European societies, and their settler offshoots overseas, moved with considerable speed from a high-mortality, high-fertility population regime to low fertility and low mortality, with major social consequences. This historic shift saw the decline of family size from approximately six children per family to fewer than two. The transition also provided the preconditions for women to move from the private sphere and constant childbearing to the public domain and the expanding industrial work force.

Explanations for this world-shaping change abounded, and a field known as demographic transition theory developed, which, while hotly contested, remains influential. Population trends, such as the post–World War II (1939–1945) “baby boom,” have shaken the theory of continuing fertility decline, yet it has remained remarkably resilient. It is clear now that demographic transition is a global phenomenon, not just a Western trend, and that since 1960 much of the world is exhibiting declining fertility, with sub-Saharan Africa probably the last to change. Most now accept that a second demographic transition is occurring (van de Kaa 1987), dating from the 1960s, as even lower birthrates, well below replacement level, prevail in several European and Asian countries. While many demographers expected that birthrates would reach the replacement level, and then plateau, now there is concern that some countries’ birthrates are so low that their societies will eventually shrink, possibly disappear.

The concern with demographic change has considerable implications for political and social decision making in relation to the family, the labor market, and immigration policy. Fertility decline has moved from being a preoccupation of demographers to a central concern for politicians and social commentators. It takes on a new urgency as low fertility leads to inevitable population ageing.

In the 1960s exponents of demographic transition theory in the West, fearful of a “population explosion,” particularly in the developing world, and eager to gain political advantage in a cold war climate, sought to apply the theory, with varying results, in developing countries through agencies such as the World Bank and the United Nations Fund for Population Activities. The birth control pill, adopted so centrally in the West, was originally funded to provide contraception in the developing world on the understanding that knowledge of birth control was all that was needed for fertility decline. Later, more considered approaches are based on the broader finding of demographic transition theory—that socioeconomic change is more likely to lead to reduced fertility.

HISTORY OF THE THEORY

Demographic transition theory is curiously paradoxical. While there is no general agreement as to its explanatory frameworks, it is constantly invoked as if there were. This is due in part to demography’s post–World War II desire to be a science and to establish a “grand theory” of population and fertility decline. Yet even in this quantitatively based discipline, wider intellectual currents have intruded: postmodernism and cultural and anthropological explanations have recently entered the field. Short-term theory is now the order of the day.

In 1937 Kingsley Davis (1908–1997), an early exponent of the theory, suggested that ultimately the reproduction of the species is incompatible with advanced industrial society. Thus he established the major framework of the theory, which held that socioeconomic development and modernization are major causal forces. It is this element of the theory that remains robust. In a 2006 volume titled Demographic Transition Theory, one of the most influential twentieth-century exponents, John C. Caldwell, argued that in industrial society the old values essential to agricultural societies—strong family, virginity, loyalty, legitimate births—are no longer necessary except as “social pacifiers.” Industrial society and, even more, postindustrial knowledge economies, need mobile, educated individuals unencumbered with babies and family ties.

Within the overarching model of socioeconomic change, there is no common acceptance of particular determinants of transformation, as different societies take varying paths to declining birthrates. The onset and tempo of mortality and fertility decline vary widely. Must a falling off in mortality precede a fertility decline? Are modern technologies of birth control essential or indeed sufficient? Is decline more likely in conjugal families (those based on husband, wife, and children) rather than the joint (extended) families of much of Asia and Africa? How critical are gender regimes? It is now overwhelmingly clear that women’s education is inversely related to fertility. The more highly educated women are, the fewer children they produce, with few exceptions. How critical is institutional change, such as government policy in relation to education, to welfare provision, and to legal frameworks (McDonald 2006)? What role does ideational change play—the decline of religious belief, the centrality of individuals and their entitlements, the significance of planning modern lives, women’s reproductive rights, and notions of consumption and leisure? All of these elements have played a significant part in variants of demographic transition theory.

Some countries (Japan, Singapore, Taiwan, as well as much of central Europe and southern Europe) now exhibit very low fertility, defined as continuing fertility under 1.5 births per woman on average, sometimes referred to as a birth strike. Most commentators agree that this is largely due to women working and to the inability of states to make women’s work and childbearing compatible. Does this low fertility foretell the future or is the experience of the United States, which since the late 1970s has exhibited a rise to replacement-level fertility, an opposing model? How significant is mode of production versus changing ideas and attitudes? Dirk van de Kaa, an influential demographer from the Netherlands, maintains that cohorts of young people with common, postmodern, individualistic ideas are implicated, whereas Caldwell insists that mode of production is primary and that neoliberalism and the accompanying insecurity it produces in the workplace play a significant role in inhibiting births.

Some theorists have predicted that the creation of a world economic system where children are of no immediate economic value to their parents will inevitably lead to lower world population—a goal much desired by environmentalists. Others point out that in much of Asia and Africa, patriarchy, a regime that puts children and lineage before women’s rights, is still dominant and that fertility decline may not be inevitable. Prediction is always fraught, and an element that has been overlooked in much twentieth-century demography may well come back to haunt us. Secularization, the decline of traditional religious belief, is a key to changing Western fertility patterns. Yet any assumption that secularization will inevitably increase is risky in the light of resurgent fundamentalisms across all religious belief systems. Anthropological demography reminds us that we are not all rational actors, and that myth, superstition, and culture are all pervasive.

Between 1965 and 2000, the fertility (as measured by the total fertility rate) of both the developing world and the whole world nearly halved (Caldwell et al. 2006, p. 13). On the basis of the United Nations World Population Prospects (2004) and other findings, demographers have predicted that global population growth will almost come to a halt by 2050, “with the Earth having around 9 billion or fewer inhabitants” (Caldwell et al. 2006, p. 316). Higher and lower projections have been offered, the latter demonstrating population halving every two hundred years—surely an unacceptable outcome. With the rate of world population growth slowing, some are turning to issues of the composition of the population.

A third demographic transition has been proposed for Europe and the United States, one that sees the ancestry of some national populations being radically and permanently altered through high levels of immigration of people with distinctively different ethnic ancestry into countries with low fertility (Coleman 2006, p. 401). This is a radical departure from previous demographic transition theory in its focus on immigration. It demonstrates, however, the resilience of the theory. The demographic transition may well continue to surprise us.

SEE ALSO Anthropology; Birth Control; Club of Rome; Demography; Development Economics; Development, Rural; Fertility, Human; Gender Gap; Health in Developing Countries; Immigration; Inequality, Gender; Malthusian Trap; Modernization; Overpopulation; Population Growth; Population Studies

BIBLIOGRAPHY

Bulatao, R. A., and John Casterline, eds. 2001. Global Fertility Transition. A supplement to Population and Development Review 127.

Caldwell, John C., Bruce K. Caldwell, Pat Caldwell, et al. 2006. Demographic Transition Theory. Dordrecht, Netherlands: Springer.

Coleman, David. 2006. Immigration and Ethnic Change in Low-fertility Countries: A Third Demographic Transition. Population and Development Review 32 (3): 401–439.

Davis, Kingsley. 1937. Reproductive Institutions and the Pressure for Population. Sociological Review 29: 289–306. Reprinted as: Kingsley Davis on Reproductive Institutions and the Pressures for Population. 1997. Population and Development Review 23 (3): 611–624.

Jones, Gavin W., Robert Douglas, John Caldwell, and Rennie D’Souza, eds. 1997. The Continuing Demographic Transition. Oxford: Clarendon.

Kertzer, David, and Tom Fricke, eds. 1997. Anthropological Demography: Toward a New Synthesis. Chicago: University of Chicago Press.

McDonald, Peter. 2006. Low Fertility and the State: The Efficacy of Policy. Population and Development Review 32 (3): 485–510.

United Nations Department of Economic and Social Affairs: Population Division. World Population Prospects: The 2004 Revision. http://esa.un.org/unpp/.

Van de Kaa, Dirk. 1987. Europe’s Second Demographic Transition. Population Bulletin 42 (1).

Alison Mackinnon

DEMOGRAPHIC TRANSITION

The term "demographic transition" denotes the effects on population of the social and economic

Figure 1

changes of the Industrial Revolution, which transformed Europe in the eighteenth and nineteenth centuries and spread to the rest of the world in the twentieth century. In simple terms the complete transition would begin with a stationary population with birth and death rates of about 30 per 1,000 persons, a triangular population pyramid, and life expectancy of about 30 years. The transition would end with a stationary population with birth and death rates of 10 per 1,000 persons, and a life expectancy close to the biological limit of 100 years. This final state was not reached by the beginning of the twenty-first century, but in some developed countries the life expectancy of females is over 80 years. Figure 1 shows an example of this transition, with data for England and Wales, the first countries to experience the Industrial Revolution.

The first effect of the transition was a reduction in the death rate, which continued throughout the transition period. The birth rate increased slightly at first, but later fell to the same lower level as the death rate. During the transition, the excess birth rate over the death rate (the rate of natural increase) produced a large increase in the size of the population. Not all European countries experienced the transition in exactly the same way. In particular, the fall in the birth rate began in France in the early nineteenth century, and later spread to other countries, not reaching Ireland and Russia until the twentieth century.

As an empirical generalization, the above model has proved to be reasonably accurate (see Figure1). By 1990 the transition to equal birth and death rates was almost completed in the developed regions of the world, especially in Europe. The transition is underway in the less-developed regions of the world, with birth rates falling steeply in all regions except sub-Saharan Africa. The world as a whole was, in 1990, at the same stage of the transition as were the developed regions in 1950.

It is generally accepted that the fall in mortality associated with industrialization was due to improved production and distribution of food, which removed the risk of famine and increased resistance to infectious disease. The risk of epidemic disease was also reduced by public health measures such as vaccination against smallpox, the control of waterborne infections by improved sanitation, and of milk-borne infections by pasteurization. Improved medical treatment had little real effect until the middle of the twentieth century.

The cause of the subsequent fall in fertility, which began in the middle of the nineteenth century, is more complex. In preindustrial societies, fertility is primarily controlled through restrictions on the age at which people can marry. Marital fertility in these societies is high, since children are a valuable resource for families involved in agriculture and domestic industries such as spinning and weaving. A fall in mortality, however, will tend to delay succession to land and hence tighten the restrictions on marriage. Improvements in health will also increase the spacing of children, primarily due to the increased survival of infants and a prolongation of the average duration of lactation. Industrialization might tend to increase fertility at first by providing opportunities for earlier marriage. However, especially after the introduction of legislation controlling the employment of children in factories, industrialization will tend to reduce the income obtained from additional children.

Gerry B. Hill

(see also: Birthrate; Chronic Illness; Demography; Epidemiologic Transition; Mortality Rates; Noncommunicable Disease Control; Population Pyramid )

Bibliography

Beaver, S. E. (1975). Demographic Transition Theory Reinterpreted. Lexington, MA: Lexington Books.

Chesnais, J. C. (1992). The Demographic Transition: Stages, Patterns and Economic Implications, trans. E. Kreager and P. Kreager. Oxford, UK: Clarendon Press.

Livi-Bici, M. (1992). A Concise History of World Population, trans. C. Ipsen. Malden, MA: Blackwell.

—— (1999). The Population of Europe, trans. C. De Nardi Ispen and C. Ispen. Malden, MA: Blackwell.

Demographic transition

Developed by demographer Frank Notestein in 1945, this concept describes the typical pattern of falling death and birth rates in response to better living conditions associated with economic development. This idea is important, for it offers the hope that developing countries will follow the same pathway to population stability as have industrialized countries. In response to the Industrial Revolution, for example, Europe experienced a population explosion during the nineteenth century. Emigration helped alleviate overpopulation, but European couples clearly decided on their own to limit family size.

Notestein identified three phases of demographic transition: preindustrial, developing, and modern industrialized societies. Many authors add a fourth phase, postindustrial. In phase one, birth rates and death rates are both high with stable populations. As development provides a better food supply and sanitation , death rates begin to plummet, marking the onset of phase two. However, birth rates remain high, as families follow the pattern of preceding generations. The gap between high birth rates and falling death rates produces a population explosion, sometimes doubling in less than 25 years.

After one or two generations of large, surviving families, birth rates begin to taper off, and as the population ages, death rates rise. Finally a new balance is established, phase three, with low birth and death rates. The population is now much larger yet stable. The experience of some European countries, especially in Central Europe and Russia, suggests a fourth phase where populations actually decline. This may be a response to past hardships and oppressive political systems there, however.

Historically, birth rates have always been high. With few exceptions population explosions are linked to declining death rates, not rising birth rates. Infants and young children are especially vulnerable; sanitation and proper food are vital. Infant survival is seen by some as a threat because of the builtin momentum for population growth . However, history reveals that there has been no decline in birth rates which has not been preceded by a drop in infant mortality . In a burgeoning world this makes infant survival a matter of top priority. To this end, in 1986 the United Nations adopted a program with the acronym GOBI: Growth monitoring, Oral rehydration therapy (to combat killer diarrhea), Breast feeding, and Immunization against major communicable diseases .

See also Child survival revolution; Population Council

[Nathan H. Meleen ]

RESOURCES

BOOKS

Cunningham, W. P., and B. W. Saigo. Environmental Science: A Global Concern. 2nd ed. Dubuque, IA: William C. Brown, 1992.

Maddox, J. The Doomsday Syndrome. New York: McGraw-Hill, 1972.

PERIODICALS

Keyfitz, N. "The Growing Human Population." Scientific American 261 (September 1989): 7-16.