The Completion of Childbearing: Change and Variation in Timing

Using data on fertility histories from the 1980 US Current Population Survey which included about 77000 households in a national probability sample the timing of the completion of childbearing (as measured by the age of the mother at her final birth) of successive 20th-Century cohorts of US women (born in 1906-15 1916-25 1926-30 and 1931-35) investigated. Data from the National Survey of Family Growth (NSFG) were also used to examine the likely age at completion of childbearing for ever-married women who had not passed the reproductive period by the time of the survey. By examining the entire distributions of age at final birth as well as summary measures a substantial cohort change in the timing of the last birth among Whites and Blacks was found that was not evident from the summary measures of central tendency and dispersion. Among Whites the cohort changes consisting of a 50% reduction in the proportion finishing reproduction later than 35 years of age were not simply due to differing completed family size and age at 1st birth. In addition with these other factors controlled in a regression analysis women who experienced marital disruption and remarriage by age 45 took longer to finish their reproduction and more educated women took less time. Such effects were not statistically significant for Blacks who have experienced large reductions in the proportions of women finishing reproduction early (age<25) and late. For younger cohorts with incomplete reproduction the likely age at 1st birth was projected using the NSFG data. For both races the projected mean age was 26.6 for the youngest White cohort and 27.8 and 25.4 for the youngest 2 Black cohorts as opposed to a range from 28.1-28.7 for the oldest cohort.