Modelling the Inverse Association between Breastfeeding and Contraceptive Use

Previous studies of the inverse association between breastfeeding and contraceptive use have relied on current status data on at least one of the variables. In this paper we suggest a new way of modelling the joint temporal association of the adoption of contraception and the termination of breastfeeding over the course of a birth interval. The approach is implemented with survey data from rural Mexico. It involves first estimating a competing-risks model in which both hazards are considered simultaneous, together with a set of relevant covariates. Conditional analyses are then carried out to estimate the hazards of each event conditional on the timing of the other. By comparing the covariates, we gauge the extent to which the occurrence of one event raises or lowers the hazard of the other. The results show that, in rural Mexico, the timing of the termination of breastfeeding and that of starting contraceptive use are closely related, and that there exists a surprisingly neat interval of 120 days in which the action takes place.     

Are simple tests of son preference useful? An evaluation using data from Vietnam

Son preference is widespread although not universal. Where it occurs it may lead to higher fertility rates. Ideally son preference should be measured in the context of a hazards or parity progression model of fertility, or a logistic model of contraceptive use. Such models require large amounts of survey data, particularly to measure the covariates. Can son preference be discerned reliably using tests which rely on more limited information? The answer is yes, based on applying eight simple tests to data from the Vietnam Living Standards Survey of 1992–93 and comparing the outcomes with the benchmark results from fuller models. Some, but not all, of the simpler tests accurately measure son preference, including estimating a simple hazards or progression parity model, the unisex sibship test, and the sibling differentials test. Received: 28 September 1995 / Accepted: 2 January 1997     

Birth Spacing and Child Survival: A Cautionary Note Regarding the Evidence from the WFS

In this paper results recently published in this journal concerning the influence of birthspacing on child survival are reviewed, and two reasons are suggested why the statistical associations observed in the data collected in the World Fertility Survey may be, at least in part, spurious. Where reporting is poor, it is argued that errors may often be responsible for a substantial portion of the association between interval length and mortality, and also for the apparent influence of the death of one child on the survival prospects of a younger sibling. Where the reported dates of birth and death are reliable but contraceptive prevalence is high, there is the problem that contraceptive practice is apt to be closely associated with other behaviour likely to have a direct effect on mortality.     

The contraceptive prevalence survey project: content and status

The United States Agency for International Development (USAID) selected Westinghouse Health Systems to carry out contraceptive surveys. The primary objectives of the Contraceptive Prevalence Surveys (CPS) are to determine periodically the levels of contraceptive use in the country; to examine the correlates of and differentials in these levels in order to assess the impact of various types of governmental and nongovernmental programs; to identify factors that will facilitate an increase in contraceptive use, particularly factors involved in program planning activities; and to institutionalize in each country the capability to design and implement studies of contraceptive prevalence, to be undertaken at regular intervals by an in-country agency. Each CPS generally collects data on the basic demographic background of the country concerned, knowledge of contraceptive methods, prior contraceptive experience and current method used, past fertility behavior and future fertility intentions, present utilization of various types of service delivery systems, perceived accessibility of contraceptives, and reasons for nonacceptance of contraception. In the CPS project, data collection and field operations have been strongly stressed. Efforts have recently been made to expand the extent and sophistication of CPS data analysis. For example, 2 countries are currently using a series of mathematical techniques called synthetic estimators to estimate subnational levels of contraceptive use by merging CPS and census data. Westinghouse, in cooperation with the University of Michigan, is currently working to develop community characteristics module for inclusion in future CPS projects.     

A components method for measuring the impact of a family planning program on birth rates

One of the major goals of family planning programs worldwide has been to reduce the level of fertility in hopes of slowing the rate of natural increase and promoting social and economic development. Such programs have now been in existence for sufficient lengths of time to have had an impact on fertility levels. In general countries with organized family planning programs, marked declines in fertility levels have been observed. The extent to which such declines may be credited to organized programs has not been rigorously measured because an appropriate research methodology has been lacking. This paper describes one method of directly linking declines in fertility levels to the contraceptive protection experienced by a population. The contribution of organized family planning programs is estimated by decomposing the amount of total contraceptive protection into within-program and outside-program sources.     

A dynamic model of the reproductive process

Summary A dynamic deterministic model of the reproductive process is presented. The model describes and analyses the effect of intermediate fertility variables on fertility. The intermediate fertility variables which are the inputs to the model, include the duration of post-partum amenorrhea, fecundability, incidence of spontaneous and induced abortion, contraceptive use and effectiveness, the distribution of age at first marriage and the age specific risks of marital disruption and remarriage. To test the validity of this model, it is fitted to data obtained from reproductive histories of 512 marriages occurring during the first half of the eighteenth century in Canada.     

基于整体网络视角的农民工避孕行为影响因素分析

本文采用2005年“深圳市外来农村流动人口调查”数据,利用社会网络分析方法从整体网络角度定量研究了农民工避孕行为的影响因素。利用p*模型从整体网络结构特征分析表明,不同层次的关系结构变量对农民工是否讨论避孕的影响不同,多数个体层次变量对是否讨论避孕有显著影响;本文从整体网络衍生出个体网络,并从衍生个体网络角度研究表明,网络规模和网络成员的避孕措施会对农民工避孕措施多元化有较为显著影响。     

Contraceptive attitude-behavior consistency in adolescence

Thornburg (1973) suggests that adolescents experience a high level of value-behavior inconsistency compared to individuals in other stages of the lifespan due to engaging in peer-oriented behavioral realms that are contrary to values shared with the parental family. Extending Thornburg's value-behavior inconsistency model to encompass contraceptive attitudes and behavior, it is predicted that contraceptive attitude-behavior inconsistency is prevalent among sexually-active adolescents, and that inconsistency would be greatest when parental and peer contraceptive attitudes are perceived to be incongruent. Analysis of a sample of 167 sexually-active adolescent females ages 13-to-18 indicates that general contraceptive attitudes are consistent with contraceptive use, whereas attitudes toward specific contraceptive methods are unrelated to contraceptive behavior. The data lend support to the predictions of Thornburg's model in that contraceptive attitude-behavior inconsistency is greatest under peer favorable/parent unfavorable and peer unfavorable/parent favorable contraceptive attitude conditions.This research was supported by a grant from the United States Department of Agriculture, Agricultural Experiment Station, University of Arizona. The data for the study were gathered in 1978 and 1979.     

A Multistate model of fecundability and sterility

This paper develops a multistate hazards model for estimating fecundability and sterility from data on waiting times to conception. Important features of the model include separate sterile and nonsterile states, a distinction between preexisting sterility and sterility that begins after initiation of exposure, and log-normally distributed fecundability among nonsterile couples. Application of the model to data on first birth intervals from Taiwan, Sri Lanka, and the Amish shows that heterogeneity in fecundability is statistically significant at most ages, but that preexisting sterility and new sterility are unimportant before age 40. These results suggest that sterility may not be an important determinant of natural fertility until later reproductive ages.     

Appropriate methods for analyzing the effect of method choice on contraceptive discontinuation

The contraceptive method chosen is an important determinant of contraceptive discontinuation. However, method choice is endogenous to contraceptive discontinuation. Using data from the 1997 Indonesia Demographic and Health Survey, we apply a multilevel multi-process model to examine the impact of method choice on three types of contraceptive discontinuation. We confirm that method choice is endogenous to the processes of contraceptive abandonment and method switching, but not failure. Ignoring the endogeneity of contraceptive choice leads to various biases in the magnitude of estimated effects of method choice on abandonment and method switching, but the general conclusions are robust to these biases.     

Net delay of next conception by contraception: A highly simplified case

Abstract A probability model, building on the work of Perrin and Sheps, is presented and applied. The model makes it possible to follow a cohort of women from a pregnancy outcome to next conception. Principal simplifying assumptions are homogeneity among women and constant fecundity. Cases treated include no contraception; a single contraceptive method practised; and a second contraceptive method practised following a first one. Expected durations to next conception may be calculated in relation to the following factors: outcome of previous pregnancy, length of anovulation, natural fecundability, time first contraceptive method is initiated, characteristics of first contraceptive (effectiveness and continuation rate), characteristics of second contraceptive, and gap between termination of first and commencing second contraceptive. By suitably pairing runs of the model, one can construct experiments in which the only differentiating factor is use and non-use of a specified contraceptive, and, by differencing the corresponding mean durations to next conception, compute the net delay of next conception produced by that contraceptive.     

Binary outcomes and endogenous explanatory variables: Tests and solutions with an application to the demand for contraceptive use in tunisia

Many demographic studies examine discrete outcomes, and researchers often suspect that some of the explanatory variables may be influenced by the same unobserved factors that determine the discrete outcome under examination. In linear models, the standard solution to this potential endogeneity bias is an estimator such as two-stage least squares. These methods have been extended to models with limited dependent variables, but there is little information on the performance of the methods in the types of data sets typically used in demographic research. This paper helps to fill this gap. It describes a simple analytic framework for estimating the effects of explanatory variables on discrete outcomes, which controls for the potential endogeneity of explanatory variables. It also discusses tests for exogeneity and joint determination of the outcomes and the explanatory variables. It summarizes the results of a Monte Carlo study of the performance of these techniques and uses these results to suggest how researchers should approach these problems in practice. We apply these methods to the examination of the impact of fertility intentions on contraceptive use, based on data from the 1988 Tunisia Demographic and Health Survey.     

中国老年人口迁移的选择性

本文利用2005年全国1％人口抽样调查数据,描述老年人口跨地市级迁移的结构特征。研究发现,我国老年人口依旧把经济发达地带、大城市作为主要迁入地,与青壮年人口迁移方向产生同构。城乡老年迁移人口在迁移动机上存在很大的差别,城市户籍老年迁移人口受家庭因素驱动更大,农村户籍老年人的迁移原因更多元。从对迁入地的影响来看,国内老年迁移人口的迁入地过于集中,将对迁入地的社会医疗服务设施等构成巨大的压力。     

How do family planning workers’ visits affect women’s contraceptive behavior in bangladesh?

In Bangladesh, family planning workers' visits reduce the costs of contraception and may increase the demand. If visits increase demand or if workers are targeting their visits, past visits by family planning workers should have a positive and significant effect on later probabilities of adopting contraceptive methods. Longitudinal data show that past visits are not significant in hazard models for adoption of contraceptive methods, whereas visits in the current round are significant. Therefore family planning workers' visits affect women's contraceptive behavior by decreasing the costs of contraception. Results of contraceptive discontinuation hazard models further support this hypothesis.     

Community-level determinants of contraceptive use in the Philippines: A structural analysis

We use household and community data from the Philippines to estimate a multilevel model of contraceptive use. We go beyond previous efforts in this field by developing a structural model that recognizes joint endogeneity and the temporal ordering of variables, by considering a wider range of community influences on fertility behavior, and by employing an econometric procedure allowing for a multilevel error structure. The results suggest that there are significant effects on fertility behavior of community-level family planning services, labor-market conditions, and infrastructure development. These results provide insights regarding the structural determinants of contraceptive use and fertility that are useful for drawing policy implications.     

Tackling Poverty-migration Linkages: Evidence from Ghana and Egypt

Are migrants able to use the migration experience to their benefit, that is to improve their livelihoods, and is this result nuanced by whether migrants are poor or non-poor? This paper explores these questions quantitatively using data on migrants and non-migrants from Ghana and Egypt. It describes the main challenges in the empirical literature and introduces a conceptual model to explore the links between migration and poverty. The empirical model accounts for the direct effects of migration on poverty and for the role of migration in moderating the dynamics of poverty. Results show the selectivity of migration with respect to subjective poverty and that migration can have a significant impact on helping people improve their livelihoods. The paper further finds that selectivity with respect to human capital depends on ‘reasons for migration’ and visa status. These findings enrich existing empirical studies by providing a clear estimation of sequential events and enable policymakers to better understand the processes behind migration and poverty.     

固定效应模型对知情选择政策影响的再验证——以已婚育龄个体避孕措施选择的变化为例

利用固定效应模型对1988-2001年全国计划生育/生殖健康调查数据进行了再次分析,以量化考察知情选择政策对中国已婚育龄个体避孕措施选择的影响。研究发现,知情选择与已婚育龄个体避孕措施选择的变化之间呈现一定的因果关联。知情选择导致了育龄个体避孕措施选择的改变,表现为短效自控型避孕措施选择的可能性随着知情选择的开展在逐步升高,而长效医控型避孕措施选择的可能性在逐步降低。     

Three methods of estimating births averted nationally by contraception

This paper compares the performance of three methods applicable to national-level demographic data of estimating births averted as a consequence of contraceptive practice. Two are based on the relationship between the general fertility rate (GFR) or total fertility (TFR) and contraceptive prevalence, while the third uses Bongaarts' proximate determinants (PD) model. Estimates of the number of births averted and the percentage by which the number would have increased in the absence of contraception are consistent between the GFR-based and TFR-based methods, but in general lower than the estimates generated by the PD-based method, except for a few high-contraceptive-prevalence countries. For 156 countries and areas around the world the estimated number of births that would have occurred in a recent year in the absence of contraception--the average of the estimates of the three methods--is approximately 230 million, which is more than the estimated 129 million births that actually occurred.     

Community and contraceptive choice in rural Thailand: A case study of Nang Rong

This paper blends quantitative with qualitative data in an investigation of community and contraceptive choice in Nang Rong, Thailand. Specifically, it develops an explanation of 1) method dominance within villages, coupled with 2) marked differences between villages in the popularity of particular methods. The quantitative analysis demonstrates the importance of village location and placement of family planning services for patterns of contraceptive choice. The qualitative data provide a complementary perspective, emphasizing the importance of social as well as physical space and giving particular attention to the structure of conversational networks.     

A mathematical model for resource allocation in population programs

The reduction of population growth rates through family planning programs is being attempted in many of the developing nations of the world. This activity lends itself aptly to mathematical modeling. Building from the well-known difference equation model of population growth, a model is constructed which integrates population dynamics, program activities, and resource consumption. The model may be used predictively to assess the outcome of various program activities. Alternatively, it may be used to determine the pattern of activities which yields the greatest reduction in births under the projected resource constraints. A further use of the model is the identification of the parameters to which predictions are most sensitive; such information provides valuable insights to those gathering the input data. The model is here applied to a family planning program currently in progress. An evaluation of the feasibility of that program’s goals is provided, as well as information on limiting resources, data sensitivity, and the most important ages for contraceptive acceptance.