Encyclopedia of SociologyVol._1

DEMOGRAPHIC TRANSITION

			Life Expectancy Patterns
	90
	80
	70
1998	60
in Years,	50
Life Expecenty	40
	30
	30	40	50	60	70	80
	Life Expecenty in Years, 1986

Figure 1

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

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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, hightechnology 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-tech- nology 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.

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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-indus- trial social structure, but this perspective clearly proved inadequate. For instance, the earliest declines did not occur in England, the most urbanindustrial 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 timeseries 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

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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 subSaharan 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,

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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 halfcentury. 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

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			Mortality and Fertility
	8
	7
	6
	5
1998	4
Rate,	3
Total Fertility	2
	1
	30	40	50	60	70	80
	Life Expecenty in Years, 1986

Figure 2

degree to which populations adopt the ‘‘Western’’	it will be a transitory (albeit spectacular) episode in
nuclear family, either through cultural diffusion	human population history.
or through autonomous changes in local social
structure.	REFERENCES

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

Bongaarts, John 1975 ‘‘Why High Birth Rates are So Low.’’ Population and Development Review 1:289–296.

Caldwell, John 1976 ‘‘Toward a Restatement of Demographic Transition Theory.’’Population and Development Review 2:321–366.

——— 1986 ‘‘Routes to Low Mortality in Poor Countries.’’ Population and Development Review 12:171–220.

Cleland, John, and Christopher Wilson 1987 ‘‘Demand Theories of the Fertility Transition: An Iconoclastic View.’’ Population Studies 41:5–30.

Coale, Ansley 1973 ‘‘The Demographic Transition.’’

International Population Conference, IUSSP. Liege, Belgium.

——— 1974 ‘‘The History of Human Population.’’ Scientific American 23:41–51.

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——— 1983 ‘‘Recent Trends in Fertility in Less Developed Countries.’’ Science 221:828–832.

———, and Roy Treadway 1986 ‘‘A Summary of the Changing Distribution of Overall Fertility, Marital Fertility, and the Proportion Married in the Provinces of Europe.’’ In Ansley Coale and Susan Watkins, eds., The Decline of Fertility in Europe. Princeton: Princeton University Press.

Davis, Kingsley 1967 ‘‘Population Policy: Will Current Programs Succeed?’’ Science 158:730–739.

Enke, Stephen 1967 ‘‘The Economic Case for Birth Control.’’ Challenge/Magazine of Economic Affairs

15:30–31.

Freedman, Ronald 1998 ‘‘Observing Taiwan’s Demographic Transition: A Memoir.’’ Research Report 98–426. Ann Arbor: Population Studies Center, University of Michigan.

Guest, Avery 1981 ‘‘Social Structure and U.S. Inter-State Fertility Differentials in 1900.’’ Demography 18:453–486.

——— and Stewart Tolnay 1983 ‘‘Children’s Roles and Fertility: Late Nineteenth Century United States,’’

Social Science History 7:355–380.

Hirschman, Charles 1994 ‘‘Why Fertility Changes.’’ Annual Review of Sociology 20:203–233.

Knodel, John 1977 ‘‘Family Limitation and the Fertility Transition: Evidence from the Age Patterns of Fertility in Europe and Asia.’’ Population Studies 32:481–510.

———, and Etienne van de Walle 1979 ‘‘Lessons from the Past: Policy Implications of Historical Fertility Studies.’’ Population and Development Review 5:217–245.

Lesthaeghe, Ron 1983 ‘‘A Century of Demographic Change in Western Europe: An Exploration of Underlying Dimensions.’’ Population and Development Review 9:411–436.

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

Matthiessen, Paul C., and James C. McCann 1978 ‘‘The Role of Mortality in the European Fertility Transition: Aggregate-level Relations.’’ In Samuel H. Preston, ed., The Effects of Infant and Child Mortality on Fertility. New York: Academic Press.

Mauldin, W. Parker, and Bernard Berelson 1978 ‘‘Conditions of Fertility Decline in Developing Countries.’’

Studies in Family Planning 9:89–148.

McKeown, Thomas 1976 The Modern Rise of Population. New York: Academic Press.

Palloni, Alberto 1981 ‘‘Mortality in Latin America: Emerging Patterns.’’ Population and Development Review

7:623–649.

Population Reference Bureau 1986 World Population

Data Sheet. Washington, D.C.

——— 1998 World Population Data Sheet. Washington, D.C.

Preston, Samuel 1975 ‘‘The Changing Relationship Between Mortality and Level of Economic Development.’’ Population Studies 29:231–248.

——— 1976 Mortality Patterns in National Populations. New York: Academic Press.

———, and Michael Haines 1991 Fatal Years: Child Mortality in Late Nineteenth-Century America. Princeton: Princeton University Press.

Razzell, P.E. 1974 ‘‘An Interpretation of the Modern Rise of Population in Europe - a Critique.’’ Population Studies 28:5–17.

van de Walle, Francine 1980 ‘‘Education and the Demographic Transition in Switzerland.’’ Population and Development Review 6:463–472.

Watkins, Susan 1991 From Provinces into Nations: Demographic Integration in Western Europe, 1870–1960.

Princeton: Princeton University Press.

AVERY M. GUEST

GUNNAR ALMGREN

DEMOGRAPHY

Demography is the study of human populations. It is an important part of sociology and the other social sciences because all persisting social aggre- gates—societies, states, communities, racial or ethnic groups, professions, formal organizations, kinship groups, and so on—are also populations. The size of the population, its growth or decline, the location and spatial movement of its people, and their changing characteristics are important features of an aggregate whether one sees it as a culture, an economy, a polity, or a society. As a result some anthropologists, economists, historians, political scientists, and sociologists are also demographers, and most demographers are members of one of the traditional social science disciplines.

Notestein, Frank 1953 ‘‘Economic Problems of Population Change.’’ Proceedings of the Eighth International Conference of Agricultural Economics, 13–31. London: Oxford University Press.

A central question for each of the social sciences is: How does the community, society, or whatever, seen as a culture, an economy, a polity, or whatever, produce and renew itself over the

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years? Formal demography answers this question for aggregates seen as populations. This formal part of demography is fairly independent of the traditional social sciences and has a lengthy history in mathematics and statistics (Smith and Keyfitz 1977; Stone 1997; Desrosières 1998). It depends on a definition of age and on the relationship of age to fertility and mortality. Those relationships certainly are socially conditioned, but their major outlines are constrained by biology.

Beyond pursuing formal demography, the task of most social scientist-demographers is detailing the relationships between demographic change and other aspects of social change. Working with concepts, methods, and questions arising from the traditions of each of the social science disciplines as well as those of demography per se, scholars have investigated the relationship between demographic changes and such social changes as those in the nature of families (Davis 1985;

Sweet and Bumpass 1987; Bumpass 1990; Waite 1995), levels of economic growth (Johnson and Lee 1987; Nerlove and Raut 1997), the development of colonialism (McNeill 1990), changes in kinship structures (Dyke and Morrill 1980), nationalism and interethnic strife (Tietelbaum and

Winter 1998), and the development of the nationstate (Watkins 1991).

FORMAL DEMOGRAPHY

At the heart of demography is a body of strong and useful mathematical theory about how populations renew themselves (Keyfitz 1968, 1985; Coale

1972; Bourgeois-Pichat 1994). The theory envisions a succession of female birth cohorts living out their lives subject to a schedule of age-specific mortality chances and age-specific chances of having a female baby. In the simplest form of the model the age-specific rates are presumed constant from year to year.

Each new annual birth cohort is created because the age-specific fertility rates affect women in earlier birth cohorts who have come to a specific age in the year in question. Thus, the mothers of a new cohort of babies are spread among previous cohorts. The size of the new cohort is a weighted average of the age-specific fertility rates. The sizes of preceding cohorts, survived to the year in question, are the weights.

As a cohort of women age through their fertile period, they die and have children in successive years according to the age-specific rates appropriate to those years. Thus, the children of a single birth cohort of women are spread over a sequence of succeeding birth cohorts.

The number of girls ever born to a birth cohort, taken as a ratio to the initial size of the cohort, is implicit in the age-specific fertility and mortality rates. This ratio, called the net reproduction rate, describes the growth rate over a generation that is implicit in the age-specific rates. The length of this generation is also implicit in the agespecific rates as the average age of mothers at the birth of the second-generation daughters. With a rate of increase over a generation and a length of the generation, it is clear that an annual rate of increase is intrinsic to the age-specific rates.

The distribution of the children of a birth cohort over a series of succeeding cohorts has an important effect. If an unusually small or large birth cohort is created, the effects of its largeness or smallness will be distributed among a number of succeeding cohorts. In each of those succeeding cohorts, the effect of the unusual cohort is averaged with that of other birth cohorts to create the new cohort’s size. Those new cohorts’ ‘‘inherited’’ smallness or largeness, now diminished by averaging, will also be spread over succeeding cohorts. In a few generations the smallness or largeness will have averaged out and no reflection of the initial disturbance will be apparent.

Thus, without regard to peculiarities in the initial age distribution, the eventual age distribution of a population experiencing fixed age-specif- ic fertility and mortality will become proportionately constant. As this happens, the population will take on a fixed aggregate birth and death rate and, consequently, a fixed rate of increase. The population so created is called a stable population and its rates, called intrinsic rates, are those implicit in the net reproduction rate and the length of a generation. Such rates, as well as the net reproduction rates, are frequently calculated for the age-specific fertility and mortality rates occurring for a single year as a kind of descriptive, ‘‘what if’’ summary.

This theory is elaborated in a number of ways. In one variant, age-specific rates are not constant but change in a fixed way (Lopez 1961). In another

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elaboration the population is divided into a number of states with fixed age-specific migration or mobility among the states (Land and Rogers 1982;

Schoen 1988). States may be geographic regions, marital circumstances, educational levels, or whatever.

In part, the value of this theory is in the light it sheds on how populations work. For example, it explains how a population can outlive all of its contemporary members and yet retain its median age, percent in each race, and its regional distribution.

The fruit of the theory lies in its utility for estimation and forecasting. Using aspects of the theory, demographers are able to elaborate rather modest bits and pieces of information about a population to a fairly full description of its trajectory (Coale and Demeny 1983). Combined with this mathematical theory is a body of practical forecasting techniques, statistical estimation procedures, and data-collection wisdom that makes up a core area in demography that is sometimes called formal demography (United Nations 1983; Shryock and Siegel 1976; Pollard, Yusuf, and Pollard 1990; Namboodiri 1991; Hinde 1998).

DEMOGRAPHIC DATA

Generating the various rates and probabilities used in formal demography requires two different kinds of data. On the one hand are data that count the number of events occurring in the population in a given period of time. How many births, deaths, marriages, divorces, and so on have occurred in the past year? These kinds of data are usually collected through a vital registration system (National Research Council 1981; United Nations 1985,

1991). On the other hand are data that count the number of persons in a given circumstance at a given time. How many never-married women age twenty to twenty-four were there on July 1? These kinds of data are usually collected through a population census or large-scale demographic survey (United Nations 1992; Anderson 1988; Anderson and Fienberg 1999). From a vital registration system one gets, for example, the number of births to black women age twenty. From a census one collects the number of black women at age twenty. The division of the number of events by the population exposed to the risk of having the event occur to them yields the demographic rate, that is, the fertility rate for black women age twenty. These

two data collection systems—vital statistics and census—are remarkably different in their character. To be effective, a vital statistics system must be ever alert to see that an event is recorded promptly and accurately. A census is more of an emergency.

Most countries conduct a census every ten years, trying to enumerate all of the population in a brief time.

If a vital registration system had existed for a long time, were very accurate, and there were no uncounted migrations, one could use past births and deaths to tally up the current population by age. To the degree that such a tallying up does not match a census, one or more of the data collections systems is faulty.

SOCIAL DEMOGRAPHY

One of the standard definitions of demography is that given by Hauser and Duncan: ‘‘Demography is the study of the size, territorial distribution and composition of populations, changes therein, and the components of such change, which may be identified as natality, mortality, territorial movement (migration) and social mobility (change of status)’’ (1959, p. 2). Each of these parts—size, territorial distribution, and composition—is a major arena in which the relationships between demographic change and social change are investigated by social scientist-demographers. Each part has a somewhat separate literature, tradition, method, and body of substantive theory.

Population Size. The issue of population size and change in size is dominated by the shadow of

Malthus (Malthus 1959), who held that while food production can grow only arithmetically because of diminishing returns to investment in land and other resources, population can grow geometrically and will do so, given the chance. Writing in a time of limited information about birth control and considerable disapproval of its use, and holding little hope that many people would abstain from sexual relations, Malthus believed that populations would naturally grow to the point at which starvation and other deprivations would curtail future expansion. At that point, the average level of living would be barely above the starvation level.

Transitory improvements in the supply of food would only lead to increased births and subsequent deaths as the population returned to its

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equilibrium size. Any permanent improvement in food supplies due to technological advances would, in Malthus’s theory, simply lead to a larger population surviving at the previous level of misery.

Although there is good evidence that Malthus understood his contemporary world quite well (Lee 1980; Wrigley 1983), he missed the beginnings of the birth control movement, which were contemporaneous (McLaren 1978). The ability to limit births, albeit at some cost, without limiting sexual activity requires important modifications to the Malthusian model.

Questions of the relationship among population growth, economic growth, and resources persist into the contemporary period. The bulk of the literature is in economics. A good summary of that literature can be found in T. P. Schultz (1981), in

Rosensweig and Stark (1997), and in a National

Research Council report on population policy

(1985). A more polemical treatment, but one that may be more accessible to the noneconomist, is offered by the World Bank (1985).

Sharing the study of population size and its change with Malthusian issues is a body of substantive and empirical work on the demographic revolution or transition (Notestein 1945). The model for this transition is the course of fertility and mortality in Europe during the Industrial Revolution. The transition is thought to occur concurrently with

‘‘modernization’’ in many countries (Coale and Watkins 1986) and to be still in process in many less developed parts of the world (United Nations

1990). This transition is a change from (1) a condition of high and stable birthrates combined with high and fluctuating death rates, through (2) a period of initially lowering death rates and subsequently lowering birthrates, to (3) a period of low and fairly constant death rates combined with low and fluctuating birthrates. In the course of part (2) of this transition, the population grows very considerably because the rate of increase, absent migration, is the difference between the birthrate and the death rate.

In large measure because of anxiety that fertility might not fall rapidly enough in developing countries, a good deal of research has focused on the fertility part of the transition. One branch of this research has been a detailed historical investigation of what actually happened in Europe, since that is the base for the analogy about what is

thought likely to happen elsewhere (Coale and

Watkins 1986). A second branch was the World

Fertility Survey, perhaps the largest international social science research project ever undertaken. This project conducted carefully designed, comparable surveys with 341,300 women in seventy-one countries to investigate the circumstances of contemporary fertility decline (Cleland and Hobcraft

1985). In 1983, a continuation of this project was undertaken under the name Demographic and Health Surveys. To date, this project has provided technical assistance for more than 100 surveys in Africa, Asia, the Near East, Latin America, and the Caribbean. For more complete information about current activities see their web site at http:// www.macroint.com/dhs/.

Scholars analyzing these projects come to a fairly similar assessment of the roots of historical and contemporary fertility decline as centering in an increased secular rationality and growing norms of individual responsibility.

Detailed investigation of the mortality side of the European demographic transition has primarily been conducted by historians. A particularly useful collection of papers is available in Schofield,

Reher, and Bideau (1991). For the United States, a particularly useful book on child and infant mortality at the turn of the twentieth century is by

Haines and Preston (1991).

The utility of the idea of a demographic transition to understand population change in the developing world has, of course, been a matter of considerable debate. A good summary of this literature is found in Jones et al. (1997).

Territorial Distribution. Research on the territorial distribution of populations is conducted in sociology, geography, and economics. The history of population distribution appears to be one of population dispersion at the macroscopic level of continents, nations, or regions, and one of population concentration at the more microscopic level of larger towns and cities.

The diffusion of the human population over the globe, begun perhaps as the ice shields retreated in the late Pleistocene, continues to the present (Barraclough 1978; Bairoch 1988). More newly inhabited continents fill up and less habitable land becomes occupied as technological and social change makes it possible to live in previously

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