Five period measures of longevity

This study provides a summary of recently proposed alternatives period measures of "longevity" and assesses whether empirical differences between these measures are consistent with predictions from analytic studies. Particular attention is given to the tempo effect. Three of the five period measures are virtually equal to one another in a simulated population in which mortality follows a Gompertz model with a constant rate of improvement. Similar results are observed among females in Denmark, England and Wales and Sweden in the last quarter century. However, these three measures differ substantially from the conventional period life expectancy when mortality changes over time. These findings are consistent with theoretical analysis by Bongaarts and Feeney (2002, 2003, 2005) which demonstrated that this deviation is caused by a tempo effect whose size varies with the rate of change in mortality.life expectancy, longevity, measures, period, tempo distortion

The causes of educational differences in fertility in Sub-Saharan Africa

This study first presents an analytic framework that describes the chain of causation linking fertility to its multiple layers of determinants. Next, this framework is applied to analyse the causes of educational fertility differences in 30 sub-Saharan African countries using data from DHS surveys. The results demonstrate that education levels are positively associated with demand for and use of contraception and negatively associated with fertility and desired family size. In addition, there are differences by level of education in the relationships between indicators. As education rises, fertility is lower at a given level of contraceptive use, contraceptive use is higher at a given level of demand, and demand is higher at a given level of desired family size. The most plausible explanations for these shifting relationships are that better-educated women marry later and less often, use contraception more effectively, have more knowledge about and access to contraception, have greater autonomy in reproductive decision-making, and are more motivated to implement demand because of the higher opportunity costs of unintended childbearing.

What can fertility indicators tell us about pronatalist policy options?

The identification and implementation of ways to avert the adverse future consequences of rapid population ageing represent urgent new public policy challenges. This paper synthesises the available knowledge on pronatalist policy options and assesses their potential impact by examining three fertility indicators: the total fertility rate, the tempo-adjusted total fertility rate and the personal ideal family size. Using recent data from thirteen European countries, the TFR is found to be lower than the ideal family size in each population. The two main reasons for this gap are tempo effects and economic, social and biological obstacles to the implementation of reproductive preferences. These factors together are estimated to average approximately 0.8 to 0.9 births per woman. Policy options to raise fertility without interfering with existing reproductive preferences are proposed. The concluding section briefly examines the impact of an increase in fertility on future trends in the old-age dependency ratio.

The Quantum and Tempo of Life-Cycle Events

This study develops and applies a general framework for the analysis of the period quantum and tempo of life-cycle events, extending methods developed previously by the authors. The existence of tempo distortions is demonstrated in selected period quantum measures such as the total fertility rate and in period tempo measures such as life expectancy. A tempo distortion is defined as an inflation or deflation of a period quantum or tempo indicator of a life-cycle event, such as birth, marriage, or death, that results from a rise or fall in the mean age at which the event occurs. Period measures derived from life tables are also found to be subject to tempo distortions. Methods to remove these tempo distortions are then developed and applied.

The end of the fertility transition in the developing world

Fertility declines are now underway in many developing countries, and the focus of the debate about future fertility trends is shifting from the early to the later phases of the transition. This study examines patterns and determinants of fertility in the developing world using UN estimates of the total fertility rates for 143 developing countries from 1950 to 2000. The main objective is to identify regularities in the past record that may provide clues to future trends. Three key findings emerge from this analysis. First, the pace of fertility decline decelerates as countries reach the later stages of the transition. In the decade immediately following the transition onset, fertility usually declines rapidly and without interruption; but once fertility drops below about four births per woman, additional reductions occur, on average, at a substantially slower pace. Second, it is highly unlikely that developing countries will converge on replacement fertility of 2.1 children per woman as is often assumed in population projections. Past transition patterns suggest that a significant number of countries will likely stall above 2.1 for periods of up to decades or will approach low fertility at a very slow pace. Third, the future course of fertility depends crucially on progress in human development and on family planning effort. The recent experience of developing countries with relatively high levels of development suggests that life expectancy near 75 years combined with literacy near 95 percent is needed on average to reach replacement. Many countries are still far from these levels of human development and have weak family planning programs, thus making further progress through the transition difficult

The fertility impact of changes in the timing of childbearing in the developing world

This study examines the role of tempo effects in the fertility declines of developing countries. These effects temporarily inflate the total fertility rate (relative to the actual fertility of cohorts of women) during periods when the age at childbearing declines and they deflate it when childbearing is postponed. An analysis of data from the World Fertility Surveys and the Demographic and Health Surveys demonstrates that fertility trends observed in many developing countries are likely to be distorted by changes in the timing of childbearing. In most countries women are delaying childbearing, which implies that observed fertility is lower than it would have been without tempo changes. This pattern is most clearly documented in Taiwan, where accurate birth statistics from a vital registration system make it possible to estimate the tempo components of fertility annually from 1978 to 1993. The small but unexpected rise in the total fertility rates in Colombia in the early 1990s is attributed to a decline in the negative tempo distortion that prevailed in the 1980s. Similar interruptions of ongoing fertility declines may occur in the future in other countries when existing negative tempo effects are removed

Late marriage and the HIV epidemic in sub-Saharan Africa

This Population Council working paper assesses the potential roles of late age at marriage and a long period of premarital sexual activity as population risk factors for HIV infection in sub-Saharan Africa. The relationship between marital status and the prevalence and incidence of HIV is examined with ecological data from 33 countries in the region and with individual-level data from nationally representative Demographic and Health Surveys in Kenya and Ghana in 2003. The ecological analysis finds a significant positive correlation between HIV prevalence and the median age at first marriage, and between HIV prevalence and the interval between first sex and first marriage. In the individual-level analysis, the risk for HIV infection per year of exposure among sexually active women is higher before than after first marriage. These findings support the hypothesis that a high average age at marriage in a population leads to a long period of premarital sex during which partner changes are relatively common, thus facilitating the spread of HIV

Household size and composition in the developing world [Arabic]

This study uses data from recent household surveys in 43 developing countries to describe the main dimensions of household size and composition in the developing world. Average household size varies only modestly among regions, ranging from 5.6 in the Near East/North Africa to 4.8 in Latin America. These averages are similar to levels observed in the second half of the nineteenth century in Europe and North America. About four out of five members of the household are part of the nuclear family of the head of the household. Household size is found to be positively associated with the level of fertility and the mean age at marriage, and inversely associated with the level of marital disruption. An analysis of trends and differentials in household size suggests that convergence to smaller and predominantly nuclear households is proceeding slowly in contemporary developing countries

Household size and composition in the developing world

This study uses data from recent household surveys in 43 developing countries to describe the main dimensions of household size and composition in the developing world. Average household size varies only modestly among regions, ranging from 5.6 in the Near East/North Africa to 4.8 in Latin America. These averages are similar to levels observed in the second half of the nineteenth century in Europe and North America. About four out of five members of the household are part of the nuclear family of the head of the household. Household size is found to be positively associated with the level of fertility and the mean age at marriage, and inversely associated with the level of marital disruption. An analysis of trends and differentials in household size suggests that convergence to smaller and predominantly nuclear households is proceeding slowly in contemporary developing countries

Long-range trends in adult mortality: Models and projection methods

This Population Council working paper has 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 indicates 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