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A regression approach to the projection of U.S. fertility based on past fertility data.

The method of fertility projection used by the U.S. Bureau of the Census involves assumptions about the ultimate cohort total fertility rate and the ultimate cohort mean age at childbearing based on recent levels of fertility and women's birth expectations. This paper provides an outline of a general regression approach to fertility projection based on past data which would generate these two ultimate cohort characteristics. The technique is illustrated by using the U.S. single-year age-specific fertility rates up to 1986 for total women and projecting them indefinitely into the future until they become stable for both calendar years and cohorts.

Adolescent↗
PubMedDate not supplied

Individual fertility rate: a new individual fertility measure for small populations.

Fertility measurement in small preindustrial societies is hampered by small numbers and the lack of some essential data. Most measures of fertility are collective and require large enough populations to permit grouped data analysis. Existing individual measures of fertility are often unsatisfactory. This paper presents a new measure of individual fertility, the Individual Fertility Rate (IFR), which is constructed by dividing parity by reproductive span in years and multiplying the product by 100. The result is a number which may be used as a dependent individual or cumulative variable to study the effects of health and socioeconomic factors on fertility.

Adult↗
PubMedDate not supplied

A scale to measure microbehaviors of oral contraceptive pill use.

The ways in which contraceptive methods are actually used is of increasing interest to researchers, clinicians, and policy makers. Although contraceptive "use" has multiple dimensions, existing indicators measure only one aspect of use or combine unidimensional measures to produce a questionable pastiche. This study uses a subsample of 612 respondents from a larger study of first-time patients at a public-health-department family planning clinic to develop a new measure. Psychometric properties of this measure are examined and discussed.

Contraception Behavior↗
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Interruption of breastfeeding by child death and pregnancy.

This paper estimates the mean monthly losses and proportionate interruptions of breastfeeding intervals due to child death and pregnancy. The paper uses a microanalytic model with stochastic risks for the basic processes of human reproduction. The model results show that a high proportion of women, depending upon mortality level and length of breastfeeding, have their breastfeeding interrupted by either child death or pregnancy. The results of this work suggest the need for caution in interpreting observed durations of breastfeeding. Child death and pregnancy causes bias in the reported length of breastfeeding, and this bias needs to be taken into account in statistical analysis.

Bias↗
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Seasonality of births in human populations.

Seasonal fluctuations in births have been observed in virtually all human populations. In this paper we re-examine the seasonality of births with two main objectives in mind. The first is to provide an overview of the basic facts about the seasonality of births, presenting new estimates of the seasonal patterns. Seasonality is an important if not dominant source of nontrend variation in births in virtually all populations, but there are dramatic and puzzling differences across countries and time periods in the pattern of seasonal variation observed in particular populations. The second purpose of the paper is to survey the leading hypotheses about birth seasonality that have appeared in the literature and to discuss the consistency of these hypotheses with observed seasonal patterns. Using our estimates of seasonal patterns along with other evidence in the literature, we conclude that no single explanation receives strong, consistent support from the data.

Delivery, Obstetric↗
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Births and cohort size.

Ahlburg (1983, 1986) tested a simple version of Easterlin's relative-cohort-size model of fertility on the basis of U.S. and Canadian post-war data. His conclusion was that the Easterlin model fits the data very well and can therefore be used for calculating forecasts. However, the model he estimated is oversimplified. In this paper an alternative specification is presented. The model is applied to Dutch fertility data. The Easterlin effect is found to affect the movement of births in the Netherlands during the period 1950-85, but a declining long-term trend in average family size proves far more important in explaining post-war births. The model forecasts a rise of births until 2000.

Adult↗
PubMedDate not supplied

Analysis of contraceptive discontinuation in six developing countries from durations of use at survey.

We conduct a cross-national study of contraceptive discontinuation among currently married nonsterilized contracepting women in Bolivia, Egypt, Kenya, Sri Lanka, Thailand, and Zimbabwe using the Demographic and Health Surveys (DHS). Since the DHS contains no true completed epochs of contraceptive use, the distribution of use times at survey is used to approximate the distribution of the completed epochs using the renewal theorem. Two techniques based on this approximation are used. The first technique uses local linear regression smoothing of a histogram estimate of the use time at survey pdf which is converted into an estimate of the discontinuation probability function. The second technique poses a proportional hazards Weibull distribution for the discontinuation probability function which is then converted into a model for the use times at survey. This second technique is used to model the observed variations in use across countries while controlling for other sociodemographic factors such as children ever born, age, and education, as well as a variable which encodes knowledge of the fertility cycle. Pill discontinuation probabilities range from 0.12 to 0.47 in the first year. IUD discontinuation probabilities range from 0.18 to 0.53 in the first year. Discontinuation probabilities in Egypt over all methods are in agreement with those reported in Ali and Cleland (1995). Logged relative risks of pill discontinuation range from -0.94 (Sri Lanka) to 0 (Kenya), while logged relative risks of IUD discontinuation range from -0.53 (Sri Lanka) to 0.41 (Zimbabwe). The ordering of risks of pill discontinuation among the six countries considered is in agreement with the ordering of total fertility rates excerpted from Westoff (1991).

Contraception Behavior↗