Testing for fertility stalls in demographic and health surveys
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RESEARCH
Open Access
Testing for fertility stalls in demographic and health surveys Michel L Garenne1,2,3
Abstract This study compares two methods for testing fertility trends and fertility stalls using Demographic and Health Surveys data. The first method is based on linear regression and uses the equivalence of period and cohort estimates with the same cumulative fertility at age 40, the same number of births, and the same distribution of women by parity. The second method is based on logistic regression. It assumes that the age pattern of fertility is constant over short periods of time. Both methods were applied to fertility trends in several African countries (Ghana, Kenya, Madagascar, Nigeria, Rwanda, Senegal, Tanzania, and Zambia). The two methods were found to predict similar values of cumulative fertility, to produce consistent slopes, to document fertility trends the same way, and to characterize fertility stalls with similar statistical evidence. They can also be used to refute apparent fertility stalls obtained when comparing two point estimates from two successive surveys. Keywords: Demographic transition, Fertility decline, Fertility stall, Statistical methods, Linear regression, Logistic regression, Poisson regression, sub-Saharan Africa
Introduction Fertility decline from high values typical of natural fertility to near- or below- replacement fertility is a quasiuniversal phenomenon. Fertility decline started in almost all countries in the world at some point in the 19th or 20th century with only a few exceptions, and the fertility transition finished (or was almost finished) in a majority of countries by 2010. The United Nations Population Division anticipates that fertility will continue to decline in the next 40 years in the world as a whole. However, the fertility transition will not be completed by 2050 in countries that are currently classified as “high fertility, “ most of them in sub-Saharan Africa. In these countries, one expects a total fertility rate (TFR) of 2.8 children per woman, whereas elsewhere fertility will be below replacement, with TFR equaling 1.8 by 2050 [1]. The transition from high levels (i.e., five to eight children per woman) to low levels of fertility (i. e., two or fewer children per woman) is usually continuous and smooth and spans approximately 60 years, or two generations. Occasionally, this transition can occur much faster (over 15 to 25 years) or slower (over a Correspondence: [email protected] 1 Institut de Recherche pour le Développement, UMI Résiliences, Paris, France Full list of author information is available at the end of the article
century or more). A typical example of a smooth fertility transition in Europe is Sweden, where the core of the transition occurred between 1870 and 1930 when the TFR dropped from 4.4 to 1.7 children per woman (corresponding cohorts are 1840 to 1900). Similar changes were found throughout Europe, with the exception of France [2,3]. However, in some cases the transition is not continuous, and long periods of fertility stal
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