The analysis of linkages in demographic theory

Many seemingly different questions that arise in the analysis of population change can be phrased as the same technical question: How, within a given demographic model, would variable y change if the age- or time-specific function f were to change arbitrarily in shape and intensity? At present demography lacks the machinery to answer this question in analytical and general form. This paper suggests a method based on modern functional calculus for deriving closed-form expressions for the sensitivity of demographic variables to changes in input functions or schedules. It uses this “linkage method” to obtain closed-form expressions for the response of the intrinsic growth rate, birth rate, and age composition of a stable population to arbitrary marginal changes in its age patterns of fertility and mortality. It uses it also to obtain expressions for the transient response of the age composition of a nonstable population to time-varying changes in the birth sequence, and to age-specific fertility and mortality patterns that change over time. The problem of “bias” in period vital rates is also looked at.     

新古典增长理论框架下的老龄化效应分析

众所周知,日益严重的老龄化进程将对一国经济和社会各个方面的产生深远影响。近年来,以OECD和亚洲国家为对象的定量研究大量涌现。着重于分析人口老龄化对中国宏观经济变量的影响,本文考察了现收现付制和取消现收现付制两种不同条件下的政策模拟。运用Ayse Imrohoroglu等人的新古典增长模型,我们的政策模拟基于两种不同的人口冲击:生育率降低、预期寿命延长。我们发现在上述政策模拟中,个体变量和汇总变量的变化各不相同。     

Capital accumulation and the sources of demographic change

We develop a neoclassical growth model having a realistic demographic structure. We identify the critical channel of impact to be the intertemporal consumption allocation decision through the “generational turnover term”. Expressing the aggregate dynamics as a generalization of the conventional neoclassical growth model provides important insights, enabling us to view in a unified way how alternative demographic structures impinge on the macrodynamic equilibrium. Using an approximation to the generational turnover term, we are able to characterize both the steady state and the local transitional dynamics. Through numerical simulations, we analyze the steady state as well as the transitional effects of structural and demographic changes.     

The United Nations on World Population in 2300

The Population Division of the United Nations biennially issues detailed population estimates and projections covering the period 1950–2050. The most recent revision of these estimates and projections, the 2002 assessment, was released in February 2003. At irregular intervals, the Population Division also publishes long‐range projections. The most recent of these, covering the period up to 2150, was issued in 2000, based on the 1998 assessment. On 9 December 2003, the Population Division released the preliminary report on a new set of long‐range projections, dovetailing with the 2002 assessment, that extend over a much longer time span: up to 2300 ( http://www.un.org/esa/population/publications/longrange2/longrange2.htm ). Unlike previous long‐range projections, which, apart from China and In‐dia, were prepared for large regional groupings only, the new projections are elaborated separately for 192 countries. Given the enormous uncertainties of the character of demographic trends over such an extended period, the information content of these projections is somewhat elusive. However, they are expected to be used to provide the demographic input for long‐range models of global climate change. Long‐range population projections also serve to demonstrate the unsustainability of certain seemingly plausible assumptions as to the future course of particular demographic parameters. In the present case, for example, the high‐fertility projection, reflecting a sustained total fertility rate at the relatively modest level of 2.35, by 2300 would yield a population of some 32 billion in the countries now classified as less developed. Or, in a yet more extreme exercise 0/reductio ad absurdum, maintaining constant fertility at present rates would result in a population size of some 120 trillion in the countries now classified as least developed. Apart from the “high fertility” and “constant fertility” models just cited, the projections are calculated for three additional instructive variants: “low fertility,”“medium fertility,” and “zero growth.” Underlying each of the five variants is a single assumption on mortality change: expectation of life at birth creeping up, country‐by‐country, to a 2300 level ranging between 88 and 106 years. International migration is set at zero throughout the period 2050‐2300 in each variant. Thus the projections are unabashedly stylized and surprise‐free, providing a simple demonstration of the consequences, in terms of population size and age structure, of clearly stated assumptions on the future course of demographic variables. Reproduced below is the Executive Summary of the preliminary report on the UN long‐range projections presented to a UN technical working group on long‐range projections at its December 2003 meeting in New York and slightly revised afterward. A full final report on this topic by the Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat will be published later in 2004.     

Modeling momentum in gradual demographic

The analysis of population momentum following a gradual decline in fertility to replacement level provides valuable insights into prospects for future population growth. Here, we extend recent work in the area by applying a new form of the quadratic hyperstable (QH) model, which relates exponentially changing fertility to the resultant exponentiated quadratic birth sequence. Modeling gradual transitions from an initial stable population to an ultimate stationary population indicates that such declines in fertility increase momentum by a product of two factors. The first factor is a previously noted continuation of stable growth for half the period of decline. The second is a not previously appreciated offsetting factor that reflects the interaction between the decline in fertility, the changing age pattern of fertility, and the changing age composition of the population. Numerical examples using both hypothetical and actual populations demonstrate that for declines of any length, the product of the two factors yields momentum values that closely agree with the results of population projections. The QH model can examine monotonic transitions between any two sets of constant vital rates. As a generalization of the fixed-rate stable model, it has great potential value in numerous areas of demographic analysis.     

山东省人口红利的过程判断及其对经济增长作用研究

在人口转变过程中。由于出生率与死亡率下降初始时间与速度的不同步,后者先于前者发生。会形成一个“中间大,两头小”有利于经济发展的人口年龄结构,人口学家称这段时期为“人口机会窗口”或“人口红利（demo-graphic dividend）”。本文根据人口类型划分标准对山东省及其区域人口红利进行了过程判断,并通过计算劳动力对经济增长的贡献率即劳动贡献率来显示人口红利对经济增长的推动作用,最后提出了充分实现山东省人口红利的途径。     

The recent rise in malay fertility: A new trend or a temporary lull in a fertility transition?

Period fertility rates show a recent rise in the fertility of the Malay population of Peninsular Malaysia that became evident in the late 1970s, after more than fifteen years of slow but steady declines. Detailed analysis of age-parity-specific fertility rates suggests that the recent rise is largely due to a “making up” of lower order births (first, second, and third) that had been postponed by a rapid increase in age at marriage. The period trend in higher order births and cohort trends of cumulative fertility from census data point to a continued reduction in completed Malay fertility. Regional analysis shows several states on the east coast with persistent high fertility, although the revolution in marital postponement is national in scope.     

Alvin Hansen on Economic Progress and Declining Population Growth

The driving forces of economic growth, according to the mainstream of classical economic thinking, are threefold: technological innovations, the opening up of new territories and discovery of new resources, and increase in population. In interaction, in an entrepreneurial market economy, these forces generate growth not only in the aggregate but also per capita. Evidence of their power was seen in the long stretch of rising living standards in the West over the nineteenth century, despite the ups and downs of the business cycle. However, the economic experience of the interwar years, and in particular the Great Depression of the 1930s, suggested that the forces were largely spent and hence that future economic prospects were gravely imperiled. The Keynesian revolution in economics was a response to the evident malfunctioning of the capitalist economic system, although the policy recipes it offered (for increasing demand and investment to levels capable of generating an equilibrium consistent with full employment of productive resources, especially labor) by no means commanded unanimity. The most prominent American contributor to and spokesman for the new line of economic analysis—often called “the American Keynes”—was Alvin H. Hansen (1887–1975), who took up his professorship of political economy at Harvard in 1937, just after the appearance of Keynes's General Theory. In that post, which he held until his retirement in 1956, he was one of the most influential economists of the era as a theorist, policy adviser, and teacher. Hansen interpreted the economic problems of the 1930s not just as the manifestation of a particularly sharp cyclical downturn, but as evidence of secular stagnation caused by the closing of the economic frontier, sluggishness in technological innovation, and, not least, “a drastic decline in population growth.” This “stagnation thesis” is most succinctly set out in his presidential address to the American Economic Association, delivered in Detroit, 28 December 1938, under the title Economic Progress and Declining Population Growth. The address is re‐produced below from the March 1939 issue of the American Economic Review. (The opening paragraphs of the address, and two paragraphs, immediately preceding the closing paragraph, in which Hansen discusses changes in US national income in the 1930s, have been omitted.) Hansen's analysis of the effects of declining population growth in many ways echoes the thesis set out by Keynes in his seminal Galton Lecture delivered to the Eugenics Society in 1937 (reprinted in the Archives section of PDR 4, no. 3): a demographic slowdown decreases opportunities for profitable investments and increases levels of attempted saving, hence pushes the economy toward a low‐growth equilibrium at which resources are underutilized and unemployment is high. Hansen puts special emphasis on demographically induced shifts in the composition of output. He suggests that, beyond its direct positive effect on investment and output, population growth also has an indirect enhancing effect on these factors by facilitating technological progress–contrary to the “older Malthusian view.” In his policy proposals Hansen was more interventionist than Keynes, advocating a more intrusive government role in the economy as a possible means of escaping the vicious cycle of low demand and high unemployment. As to government action to reverse demographic trends seen as deleterious, neither Keynes nor Hansen argued for policies to increase fertility, presumably because they saw them as both inappropriate and, in comparison to remedial economic policy measures, inefficient or unfeasible. The demands of the war economy in the years following Hansen's address took care of the employment problem, and the immediate postwar decades brought the stimuli of pent‐up consumer demand, an outpouring of technological innovations, a reopening of the economic frontier produced by a more liberal trade regime, and, also, an acceleration of population growth. The result was rapid overall economic growth and increasing levels of per capita income. Keynesian demand management played some role in this economic success story: by the end of the 1960s even US President Richard Nixon pronounced himself a Keynesian. But it offered no remedy for the stagflation that eventually followed. The growth‐promoting recipes favored in the last decades of the century (especially in the most successful developing economies) were anything but Keynesian: limited government, fiscal restraint, and globalization. Yet recent and anticipated demographic trends, especially in Europe—notably fertility decline and population aging—make Hansen, once again, interesting reading. Commitments of the modern welfare state for health care, retirement pensions, and job security command wide approval, but they have boosted governments' weight in the economy and made labor markets inflexible, unemployment high, and retirement early—developments that may increasingly impose a brake on economic growth and on improvements of living standards. Reform measures to ease these burdens are, in principle, straightforward, but their immediate social costs are heavy and their rewards are delayed, hence resistance to reform is strong and growing. This is likely to stimulate the search for alternative policies that offer politically more palatable tradeoffs—some of which may turn out to have an unmistakably Hansenian flavor. As to future population trends, Hansen, despite his reference to a “drastic decline in population growth” based on a comparison of nineteenth‐ and twentieth‐century Western demographic change, envisaged a convergence to a stationary population or a tendency toward very slow decrease. Yet some economies are already locked into a demographic pattern that augurs sharper declines and more rapid population aging, enhancing the relevance of the issues posed by Hansen. In Germany, for example, in the absence of immigration, the population between ages 20 and 40 will decline from 21.6 million in 2005 to 16.3 million in 2025—a drop of 23 percent. Over the same time period, the population aged 60 and older will grow from 20.5 million to 25.8 million—an increase of 26 percent. Serious efforts to slow population decline and retard population aging by stimulating fertility would of course add another major burden to government budgets.     

In Living Memory: The Demographic Dynamics of Event Recollection in a Stable Population*

We model a stable population that has experienced an important historical event and the declining proportion, as time passes, of the population that remembers that event. The proportion is determined by the demographic characteristics of the population, including its age distribution, the natural rate of growth, the underlying birth rate, the life table probabilities to which the population is subject, and the effects of immigration and emigration under alternative assumptions about the nature of the event. (We distinguish between “local” and “universal” events.) It is determined also by the choice of an age of awareness of children at the time the event occurred. We preface development of the model by noting examples of major events of the kind we have in mind and, after development, explore the model's sensitivity to different parameter specifications by experimental simulation. The output of each experiment is a sequence of “remembering” proportions at successive decade intervals and the corresponding mean ages of the “rememberers” in relation to the overall mean age of the population.     

China's demographic dilemmas

The year 2000 marks the end of a tumultuous century in China's population history, which weathered the demographic effects of devastating famines, wars, and epidemics and population growth and change. This paper examines the effect of population policies on the demographic dilemmas of China. In the 1950s, China had seen the fastest demographic transition in history, with a dramatic decline in mortality rates, followed by a decrease in fertility rates. However, in the 1970s, revisions in population control measures, changes in age structure, and fluctuations in age at marriage resulted in lower fertility rates. The struggles encountered by China in regulating fertility are described; these include the different methods of birth control, gender preference, marriage, population aging, and minority populations. Population and development issues within the context of urbanization, employment, education, health care, economy, and environment are also discussed. Future implications of these findings indicate the need for a systematic, effective, and complete environmental clean-up, as well as fertility and population policies.     

Is the Demographic Dividend an Education Dividend?

The effect of changes in age structure on economic growth has been widely studied in the demography and population economics literature. The beneficial effect of changes in age structure after a decrease in fertility has become known as the “demographic dividend.” In this article, we reassess the empirical evidence on the associations among economic growth, changes in age structure, labor force participation, and educational attainment. Using a global panel of countries, we find that after the effect of human capital dynamics is controlled for, no evidence exists that changes in age structure affect labor productivity. Our results imply that improvements in educational attainment are the key to explaining productivity and income growth and that a substantial portion of the demographic dividend is an education dividend.     

An econometric and neoclassical analysis of the timing and spacing of births in Canada from 1950 to 1990

This paper estimates a reduced form neoclassical model of Canadian fertility dynamics using an econometric technique that integrates several features not usually found in the demographic and economic literature. We find considerable support for the neoclassical model. We also find that correlated unobservables and parity stopping effects play an important role in Canadian fertility dynamics as well as other socio-demographic features of Canadian women. However, we fail to totally characterize the important drops in the fertility rate that took place for this era. Received: 2 May 1996 / Accepted: 27 March 1997     

The UN Population Division on Replacement Migration

The most salient demographic trend pictured by the influential set of population projections prepared by the Population Division of the United Nations (a unit in the UN's Department of Economic and Social Affairs) is the continuing substantial increase—albeit at a declining rate—of the global population during the coming decades. According to the “medium” variant of the most recent (1998) revision of these projections, between 2000 and 2050 the expected net addition to the size of the world population will be some 2.85 billion, a figure larger than that of the total world population as recently as the mid‐1950s. All of this increase will occur in the countries currently classified as less developed; in fact, as a result of their anticipated persistent below‐replacement levels of fertility, the more developed regions as a whole would experience declining population size beginning about 2020, and would register a net population loss of some 33 million between 2000 and 2050. A report prepared by the UN Population Division and released on 21 March 2000 addresses some of the implications of the changes in population size and age structure that low‐fertility countries will be likely to experience. The 143‐page report, issued under the eyecatching title Replacement Migration: Is It a Solution to Declining and Ageing Populations?, highlights the expected magnitude of these changes by the imaginative device of answering three hypothetical questions. The answer to each of these questions is predicated on the assumption that some specified demographic feature of various country or regional populations would be maintained at the highest level that feature would exhibit, in the absence of international migration, in the United Nations' medium population projections (as revised in 1998) during the period 1995–2050. The selected demographic features are total population size, the size of the working‐age population (15–64 years), and the so‐called potential support ratio: the ratio of the working‐age population to the old‐age population (65 years and older). The illustrative device chosen for accomplishing the specified feats of preserving the selected demographic parameters (i.e., keeping them unchanged up to 2050 once their highest value is attained) is international migration. Hence the term “replacement migration.” Given the low levels of fertility and mortality now prevailing in the more developed world (and specifically in the eight countries and the two overlapping regions for which the numerical answers to the above questions are presented in the report), and given the expected future evolution of fertility and mortality incorporated in the UN population projections, the results are predictably startling. The magnitudes of the requisite compensatory migration streams tend to be huge relative both to current net inmigration flows and to the size of the receiving populations; least so in the case of the migration needed to maintain total population size and most so in the case of migration needed to counterbalance population aging by maintaining the support ratio. Reflecting its relatively high fertility and its past and current record of receiving a large influx of international migrants, the United States is a partial exception to this rule. But even for the US to maintain the support ratio at its highest—year 1995—level of 5.21 would require increasing net inmigration more than tenfold. The country, the report states, would have to receive 593 million immigrants between 1995 and 2050, or a yearly average of 10.8 million. The extreme case is the Republic of Korea, where the exercise calls for maintaining a support ratio of 12.6. To satisfy this requirement, Korea, with a current population of some 47 million, would need 5.1 billion immigrants between 1995 and 2050, or an average of 94 million immigrants per year. (In the calculations, the age and sex distribution of migrants is assumed to be the same as that observed in the past in the main immigration countries. The fertility and mortality of immigrants are assumed to be identical with those of the receiving population.) The “Executive Summary” of the report is reproduced below, with the permission of the United Nations. Chapters of the full report set out the issues that prompted the exercise; provide a selective review of the literature; explain the methodology and the assumptions underlying the calculations; and present the detailed results for the eight countries and two regions selected for illustrative purposes. A brief discussion of the implications of the findings concludes the report. As is evident even from the figures just cited, immigration is shown to be at best a modest potential palliative to whatever problems declining population size and population aging are likely to pose to low‐fertility countries. The calculations, however, vividly illustrate that demographic changes will profoundly affect society and the economy, and will require adjustments that remain inadequately appreciated and assessed. The criteria specified in the UN calculations—maintenance of particular demographic parameters at a peak value—of course do not necessarily have special normative significance. Past demographic changes, with respect notably to the age distribution as well as population size, have been substantial, yet they have been successfully accommodated under circumstances of growing prosperity in many countries. But the past may be an imperfect guide in confronting the evolving dynamics of low‐fertility populations. As the report convincingly states, the new demographic challenges will require comprehensive reassessments of many established economic and social policies and programs.     

A Population Policy Rationale for the Twenty‐First Century

I propose that the primary goal of twenty‐first‐century population policies should be to strengthen the human resource base for national and global sustainable development. I discuss the shortcomings of the three dominant twentieth‐century population policy rationales: acceptance of replacement‐level fertility as a demographic goal; realizing a “demographic dividend” from the changing age structure; and filling the “unmet need” for family planning. I demonstrate that in all three cases the explicit incorporation of education into the model changes the picture and makes female education a key population policy priority. Population policies under this new rationale could be viewed as public human resource management. I argue that 20 years after the Cairo ICPD the international community needs a new rationale for population policies in the context of sustainable development and that a focus on human capital development, in particular education and health, is the most promising approach.     

D. V. Glass on the Problems of a Declining Population

During the past quarter century fertility has dropped below replacement levels in many parts of the world. According to United Nations estimates, in 2005 this was the case in 65 countries, comprising 43 percent of the world's population. In many cases, most notably in Europe and East Asia, the shortfall of fertility from the level that would be necessary in the long run to sustain a stationary population is substantial. In Europe, for example, the average total fertility rate for the period 2000–2005 was 1.4. Indefinite maintenance of such a level implies a shrinkage of the total population by one‐third over a generation–roughly every 30 years. Accompanying that rapid decline of total numbers would be an age structure containing a preponderance of the elderly, posing extreme adjustment difficulties for the economic and social system. Societies that wish to avoid radical depopulation would have to engineer a substantial rise infertility–if not to full replacement level (slightly more than two children per woman), then at least to a level that would moderate the tempo of population decline and make population aging easier to cope with. An additional counter to declining numbers, if not significantly to population aging, could come from net immigration. This is the demographic future assumed in the UN medium‐variant projections for countries and regions currently of very low fertility. Thus, for example, in Europe over the period up to 2050 fertility is assumed to rise to 1.85 and net immigration to amount to some 32 million persons. The UN projections also anticipate further improvement in average life expectancy–from its current level of 74 years to 81 years. This factor slows the decline in population size but accelerates population aging. Under these assumptions, Europe's population would decline from its present 728 million to 653 million by 2050. At that time the proportion of the population over age 65 would be 27.6 percent, nearly double its present share. Demographic change of this nature is not a novel prospect. It was envisioned in a number of European countries and in North America, Australia, and New Zealand in the late 1920s and early 1930s. Concern with the possible economic and social consequences generated much discussion at that time among demographers and social scientists at large and also attracted public attention. Possible policy measures that might reverse the downward trend of fertility were also debated, although resulting in only hesitant and largely inconsequential action. The article by D. V. Glass reproduced below is an especially lucid and concise treatment of demographic changes under conditions of low fertility and their economic and social implications. It appeared in Eugenics Review (vol. 29, no. 1, pp. 39–47) in 1937 when the author was 26 years old. Glass's line of argument is broadly representative of the main focus of demographic analysis in the mid‐1930s on aspects of population dynamics, applying the then still novel analytical tool of the stable population model. It also echoes the work of economists then witnessing the great difficulties capitalist economies faced in adjusting to structural changes in consumer demand and labor supply. While Glass addresses these issues primarily with reference to England and Wales, he sees the issues as affecting all industrialized countries. The Malthusian problem of relentless population growth he persuasively declares to be irrelevant for these countries. The Western world faces the opposite problem: population decline, a trend only temporarily masked by the effects of an age distribution that still has a relatively high proportion of women in the child‐bearing ages, reflecting the higher fertility level of the past. A stationary population, Glass cogently argues, is to be welcomed, and he considers the absolute size at which zero growth would be achieved relatively unimportant. In contrast, a continuous population decline would have “thoroughly disastrous” results in an individualist civilization and in “an unplanned economic system.” And, he concedes, somewhat quaintly, that sustained below‐replacement fertility would pose a great problem “even in a country in which the means of production were owned communally.” Glass's conclusions about the reversibility of low fertility are as pessimistic as those of most informed observers today. Still, he sees hope in a future “rationally planned civilization” that would “produce an environment in which high fertility and a high standard of life will both be possible.” In this context, high fertility means the level necessary to sustain the population in a stationary state. By present‐day standards the level Glass calculates as needed for long‐term zero growth is indeed fairly high: 2.87 children per woman. But that figure reflects the fact that, when he wrote, mortality up to age 50 was still fairly high and fertility occurred almost wholly within marriage; it also assumes zero net immigration. In the last 70 years much has changed in each of these three components of population dynamics, both in England and Wales and in the rest of Europe. Still, Glass's commentary remains highly relevant to the discussion of the problems of low fertility today. David Victor Glass (1911–78) was associated with the London School of Economics throughout much of his scientific career. He followed R. R. Kuczynski as reader in demography in 1945 and became professor of sociology in 1948. His work on demography, population history, and population policy had already made him one of the most influential demographers in pre‐World War II Britain. After the war he rose to international prominence through pioneering work on the Royal Commission of Population; through his research on historical demography, the history of demographic thought, and social mobility; and through founding, in 1947, the journal Population Studies, which he edited until his death.     

Age structure,growth, attrition and accession: A new synthesis

This paper shows that each equation describing relationships among demographic parameters in a stable population is a special case of a similar and equally simple equation that applies to any closed population and demonstrates some implications of these new equations for demographic theory and practice. Much of formal demography deals with functions that pertain to individuals passing through life, or to a stationary population in which births of individuals are evenly distributed over time. These functions include life expectancy, probabilities of survival, net and gross reproduction rates, expected years spent in various states and the probability that certain events will occur in the course of life. The stable population model permits the translation of population structure or processes in a more general type of population, with constant growth rates, back into equivalent populations for a stationary population. The method for translation developed in this paper, requiring only a set of age-specific growth rates is even more general, applying to any population. Age specific growth rates may also be useful for performing reverse translations, between a population's life table and its birth rate or its age distribution. Tables of numbers of females by single years of age in Sweden are used to illustrate applications. Tables summarize the basic relations among certain functions in a stationary population, a stable population and any population. Applications of new equations, particularly to demographic estimation of mortality, fertility and migration, from incomplete data, are described. Some other applications include; the 2 sex problem, increment decrement tables, convergence of population to its stable form, and cyclical changes in vital rates. Stable population models will continue to demonstrate long term implications of changes in mortality and fertility. However, in demographic estimation and measurement, new procedures will support most of those based on stable assumptions.     

México's demographic transition: Public policy and spatial process

A logistic growth equation is used to model México's epidemiological and fertility transitions, creating variables used to model the spatial diffusion of demographic change across the states. Consistent with the goals of the Lázaro Cárdenas administration, the epidemiological transition unfolded uniformly across the states, accessible to rich and poor alike, but the urban-oriented family planning programs introduced by Luis Echeverria have favored elites, have diffused selectively, and have ensured that the burdens of the population explosion have borne down most heavily on the poor and the remote. Betsy Brewer, Cyprain Engwenyi, Mark Frank and Mark Frost also provided research assistance.     

Bridewealth and Birth Control: Low Fertility in the Indonesian Archipelago, 1500–1900

Before the onset of the present demographic transition, population growth in Indonesia had reached unprecedentedly high levels. This article demonstrates that such high levels were a recent phenomenon. Prior to 1900 rates of natural population increase were low to very low in most areas in Indonesia. This runs counter to expectations based on Hajnal's “Eastern marriage pattern,” which could imply high growth levels in extended family areas, such as most Indonesian regions outside Java in the past. Usually, the low population growth rates in Southeast Asia are attributed to high mortality owing to high levels of violent conflict. It is argued that other factors contributing to such high levels of mortality should receive more attention. In this article it is also argued that low fertility rates, too, played a role in generating low rates of natural increase. The article discusses the influence of marriage patterns, household structure, methods of birth control, adoption, and slavery on fertility.     

A Cohort Model of Fertility Postponement

We introduce a new formal model in which demographic behavior such as fertility is postponed by differing amounts depending only on cohort membership. The cohort-based model shows the effects of cohort shifts on period fertility measures and provides an accompanying tempo adjustment to determine the period fertility that would have occurred without postponement. Cohort-based postponement spans multiple periods and produces “fertility momentum,” with implications for future fertility rates. We illustrate several methods for model estimation and apply the model to fertility in several countries. We also compare the fit of period-based and cohort-based shift models to the recent Dutch fertility surface, showing how cohort- and period-based postponement can occur simultaneously.