Speed of reproduction

The research objective was to examine with data from less developed societies fertility variation in what is identified as the 6 basic demographic dimensions: age; duration; historical period; age at entry; birth cohort; and entry cohort. The fertility data are from 9 less developed countries which have participated in the World Fertility Survey (WFS) program i.e. Bangladesh Colombia Indonesia Jamaica Jordan Kenya Korea Mexico and Sri Lanka. The following were among the main study findings: 1) age and duration since entry (to marriage or motherhood) were the dominant demographic dimensions in the fertility rates analyzed with historical period of lesser but still considerable importance; 2) patterns of age and duration effects were very similar across countries with the age patterns more heterogeneous than the duration patterns; 3) pattern of period effects varied more across countries than age and duration patterns in part the result of differences among countries in fertility trends in the years before the WFS survey; 4) significant birth cohort and/or entry cohort effects on fertility tempo were evident for a majority of countries especially those in which reproductive behavior has been in transition; 5) direct effects of age at entry and interactive effects of age at entry and duration since entry were small or nonexistent; 6) educational attainment affected reproductive timing in every country; and 7) fertility rates of never users presented a simpler structure and for these women period affects were attenuated or absent altogether. The main finding of the analysis was the emergence of age and duration as the dominant demographic dimensions of reproduction. These 2 are the dimensions in which fertility varies. The results are unambiguous about the existence of effects of age and duration net of each other in societies where fertility is highly controlled and in those where there is thought to be little fertility control. The fact that both age and duration are required implies that the demographic dimensions are insufficiently controlled in most analyses. More unexpected was the finding that cross national variations in fertility control appear to be captured better by age than by duration.