John Bongaarts

A framework for analyzing the proximate determinants of fertility

Studies of the causes of fertility levels and their changes often seek to measure directly the impact of socioeconomic factors on fertility. Such procedures have a broad appeal to policymakers, offering as they do to pinpoint mechanisms susceptible to manipulation by official policy. Despite this appeal, such approaches are considerably more problematical in their application. Not infrequently, relationships are found to differ not only in magnitude but even in direction in different settings and at different times. Substantial insights can be gained if, in addition to the socioeconomic factors influencing fertility, the specific mechanisms through which these factors operate are identified. For example, the level of education of women is a socioeconomic indicator that is frequently found to be negatively related to fertility. A more detailed analysis may show that among educated women marriage is relatively late or the use of contraception more frequent, thus clarifying the relationship between education and fertility. In general, the biological and behavioral factors through which socioeconomic, cultural, and environmental variables affect fertility are called intermediate fertility variables. The primary characteristic of an intelmediate fertility variable is its direct influence on fertility. If an intermediate fertility variable, such as the prevalence of contraception, changes, then fertility necessarily changes also (assuming the other intermediate fertility variables remain constant), while this is not necessarily the case for an indirect determinant such as income or education. Consequently, fertility

Social interactions and contemporary fertility transitions.

This analysis of fertility transition is conducted among 69 developing countries during 1960-90. It is argued that the relationship between socioeconomic development and the timing and pace of fertility decline is related to level of development regional progress in fertility decline and social interaction. The empirical test is based on the theoretical framework of Notestein and successors. Analysis is based on the UN human development index (HDI) during 1960-85 (life expectancy GDP and literacy). Findings indicate that there is a highly significant negative and nonlinear relationship between HDI and fertility. Fertility was highest among countries with low HDI scores. When HDI was over 0.7 all countries were in transition but there was no fixed threshold for entry into transition. Fertility varied widely among countries at any given level of development. Statistically significant findings and graphic presentation indicate that countries with levels of development over 0.3 in 1960-65 had higher fertility than countries with an HDI of 0.3 in 1985-90. The relationship between fertility and development shifted over time. Transition occurred first in the most industrialized literate and urban provinces of a macroregion and then other provinces in geographic proximity followed regardless of HDI level. Logistic models indicate that development level and years since the beginning of transition in the region were good predictors of transition status in Asia Latin America and Europe. The most rapid declines in fertility occurred in countries that had high levels of development at the onset of transition. How family planning affects the pace and timing of fertility decline cannot be determined. It is posited that the addition of social interaction (ideas evaluation of the merits of ideas social influence and local national and global channels of social interaction) measures to the empirical model would further explain the timing and pace of fertility transition.

Fertility, Biology, and Behavior: An Analysis of the Proximate Determinants

Fertility, Biology, and Behavior: An Analysis of the Proximate Determinants presents the proximate determinants of natural fertility. This book discusses the biological and behavioral dimensions of human fertility that are linked to intermediate fertility variables. Organized into nine chapters, this book begins with an overview of the mechanisms through which socioeconomic variables influence fertility. This text then examines the absolute and relative age-specific marital fertility rates of selected populations. Other chapters consider the trends in total fertility rates of selected countries, including Colombia, Kenya, Korea, Indonesia, Mexico, Pakistan, France, and United States. This book discusses as well the effects of deliberate marital fertility control through contraception and induced abortion. The final chapter deals with the management of sex composition and implications for birth spacing. This book is a valuable resource for reproductive physiologists, social scientists, demographers, statisticians, biologists, and graduate students with an interest in the biological and behavioral control of human fertility.

The fertility-inhibiting effects of the intermediate fertility variables.

Based on the application of an aggregate reproductive model, this study demonstrates that a small number of intermediate fertility variables are responsible for most of the variation in fertility levels of populations. Four variables--proportion married, contraception, induced abortion, and postpartum infecundability--are generally the most important determinants of fertility; the other intermediate factors are of less interest except in unusual circumstances. These four factors explain 96 percent of the variance in the total fertility rate in a sample of 41 populations that include developing and developed countries as well as historical populations. In the last section, the average fertility effect of the principal intermediate fertility variables is estimated for groups of contemporary populations with different total fertility rates.

First births in America: changes in the timing of parenthood.

Americans today are becoming parents at older ages; more of them are also remaining childless. This book addresses what causes some members of the population to choose delay or permanent childlessness how far they pervade American society and how their parenthood schedules compare with those in other developed countries. The authors bring a wide variety of data sources to bear on the question of whether these delays will be greater and permanent childlessness more widespread in the future; they employ vital registration data cross-sectional studies and longitudinal surveys. It is concluded that few young Americans intend to remain childless but that the competition of educational and career goals and the presence of unfavorable economic conditions lead to postponement of childbearing. Similar parenthood schedules were recorded during the Great Depression. The authors refute the prediction that present trends will continue in the future. Strong period effects have occurred and are likely to occur again; they are unpredictable by their very nature. Although period changes in parenthood timing appear to affect virtually all sectors of the American population there are also important exceptions. Recent divergence between white and black behavior is 1 and the persistence of very early parenthood in both good and poor times is another. Contrasts with Japan show that the parenthood schedules of contemporary Americans are not an inevitable outcome of the forces of economic development and modernization. Rather the American pattern is 1 possible response that is consistent with its culture institutions and past history.

Long-Range Trends in Adult Mortality: Models and Projection Methods

In the study reported here, I had two objectives: (1) to test a new version of the logistic model for the pattern of change over time in age-specific adult mortality rates and (2) to develop a new method for projecting future trends in adult mortality. A test of the goodness of fit of the logistic model for the force of mortality indicated that its slope parameter is nearly constant over time. This finding suggests a variant of the model that is called the shifting logistic model. A new projection method, based on the shifting mortality model, is proposed and compared with the widely used Lee-Carter procedure.

Trends in unwanted childbearing in the developing world.

This study analyzes trends in unwanted fertility in 20 developing countries, based on data from the World Fertility Surveys and the Demographic and Health Surveys. Although wanted childbearing almost invariably declines as countries move through the fertility transition, the trend in unwanted fertility was found to have an inverted U shape. During the first half of the transition, unwanted fertility tends to rise, and it does not decline until near the end of the transition. This pattern is attributed to the combined effects of an increase in the duration of exposure to the risk of unwanted pregnancy and a rise in contraceptive use as desired family size declines. The substantial variation in unwanted fertility among countries at the same transition stage is caused by variation in the degree of implementation of preferences, the effectiveness of contraceptive use, the rate of induced abortion, and other proximate determinants, such as age at marriage, duration of breastfeeding, and frequency of sexual relations. The principal policy implication from this analysis is that vigorous efforts to reduce unwanted pregnancies through family planning programs and other measures are needed early in the fertility transition because, in their absence, unwanted fertility and abortion rates are likely to rise to high levels.

Completing the fertility transition in the developing world: The role of educational differences and fertility preferences

This study summarizes patterns of educational differentials in wanted and unwanted fertility at different stages of the fertility transition. The data are from Demographic and Health Surveys in 57 less developed countries. As the transition proceeds, educational differentials in wanted fertility tend to decline and differentials in unwanted fertility tend to rise. An assessment of fertility patterns in developed and less developed countries with low fertility concludes that these differentials are likely to remain substantial when less developed countries reach the end of their transitions. This conclusion implies that the educational composition of the population remains a key predictor of overall fertility in late transitional countries and that low levels of schooling can be a cause of stalling fertility.

Late marriage and the HIV epidemic in sub-Saharan Africa

The causes of large variation in the sizes of HIV epidemics among countries in sub-Saharan Africa are not well understood. Here we assess the potential roles of late age at marriage and a long period of premarital sexual activity as population risk factors, using ecological data from 33 sub-Saharan African countries and with individual-level data from Demographic and Health Surveys (DHS) in Kenya and Ghana in 2003. The ecological analysis finds a significant positive correlation between HIV prevalence and median age at first marriage, and between HIV prevalence and interval between first sexual intercourse and first marriage. The individual-level analysis shows that HIV infection per year of exposure is higher before than after first marriage. These findings support the hypothesis of a link between a high average age at marriage and a long period of premarital intercourse during which partner changes are relatively common and facilitate the spread of HIV.

Demographic foundations of family change.

As a result of the decline in mortality current cohorts have the theoretical potential to spend more time in the conjugal family statuses of parent child and spouse. To determine the extent to which this potential has been realized in the US a model was developed to simulate demographic conditions in 1800 1900 1960 and 1980 and then calculate how long women remained in the various family statuses in each historical period. Despite declines in fertility and increases in divorce the 1980 simulated cohort spent more years as children as parents as currently married spouses and in conjugal family units than people in the 1800 and 1900 cohorts. The 1980 cohort spent about 27 adult years with spouse and surviving children--4 years more than the 1800 cohort. The proportion of adult life spent in the status as child of at least one parent over 65 years of age has increased from 15% in 1800 to 29% in 1980. On the other hand time spent as a spouse is far lower than its potential. If 1800 marriage patterns obtained concurrently with 1980 mortality years married would increase from 27 to 45 whereas the actual 1980 figure is 35 years. If 1800 mortality were combined with 1980 marriage patterns 15 of the 1980 years married would be lost showing the preponderant effect of mortality. Compared to earlier cohorts contemporary cohorts have chosen to spend a smaller proportion of their adult years as a spouse as a parent of a young child and as a member of a conjugal family unit. Time spent with spouse and children declined from 56% of adult lifetime in 1800 to 43% in 1980. The proportion of lifetime spent as a parent of a child under 18 years has declined by half and that spent as a parent of a child under 5 years has declined by 2/3 as a result of reductions in family size preferences. More attention is urged to the changing time spent in various family statuses as a potential source of social change.