Fertility measurement : a report.

  • United States. National Committee on Vital and Health Statistics.
Date:
1965
Catalogue details

Licence: Public Domain Mark

Credit: Fertility measurement : a report. Source: Wellcome Collection.

    11/36 (page 3)
    CONCLUSIONS AND RECOMMENDATIONS The following are conclusions from this study with appropriate recommendations: 1. A Change in Fertility Has Been Developing in the United States> There is no doubt about the decline in period fertility rates during the past several years. All the currently published measures portray this decline. The high birth rates following World War II had been associated with earlier age at marriage, early family formation, and an increase in the average size of the family. The change in fertility after 1957 was due partly to changes in the age composition of the population: in 1960 there were over 1 million fewer women in the most fertile age group (20-29 years) than in 1950. The decline in the birth rate was due alsoto lower age-specific ratés after 1957. It seems probable that during the remainder of this decade the age-specific birth rates above age 30 years will continue to decline and that rates below age 30 may decline or stabilize at their current levels. The trend to- ward earlier marriages has ceased. For reporting States the median age of brides at first marriage leveled off at 19.9 years after 1958, andthe median age of grooms at first marriage leveled off at 23 years, or slightly under, after 1959. The trend toward younger childbearing may have reached a limit; the median age of mothers at the birth of the first child is still low but has leveled off since 1960 at 21.4 years. bDefinition of fertility. Formany years in the United States the general term fertility has been taken to refer to the actual number of children born within a given time period, by a given age, or during a lifetime. As such it is distinguished from fe- cundity, which related to the physiological capacity to repro- duce. The fertility or the reproductive performance of an ag- gregate of individuals may be expressed as a rate or as rates, each rate having a numerator of live births occurring to a spe- cific population in a specified time period and a denominator of a number of persons, women, or person-years of exposure with the same specifications. In this sense fertility is the rate at which children are born in a given population within a given time period or to a cohort of women by a given age or over a lifetime. Cohort fertility data indicated that the trend toward higher completed fertility may be ap- proaching an upper limit. Data on expectations of women onthe number of children they expect to have in the next few years show that more recent cohorts (those of 1936-42) expect fewer children than those of 1931- 35. It now appears likely that complete fertility will stabilize or decline slightly among cohorts born in the late 1930's and early 1940's. Because of the complexity of the problem it is not possible to suggest specific types of data that will give definitive answers to questions regarding future trends in period or cohort fertility. Major political, economic, and social changes could bring unpredictable changes in marriage rates, birth rates, and family size. In regard to the immediate future, increased numbers of potential parents are beginning to enter the picture as a result of the large con- tingents of babies born following World War I. The rates at which these groups will marry and raise families are not known, Period measures provide only slight clues about future trends. The main indication of future developments in cohort fertility is that afforded by data on expectations regarding number of children. Il. Currently Published Measures Are Adequate to Reflect Certain Changes in Fertility but Require Improvement and Refinement Currently published national birth rates indi- cate the existence of changes in period fertility. A deficiency in these data, and one which makes interpretation difficult, is the lack of information on the marital characteristics of the population. Data such as age at marriage and duration of marriage for the parents and for the total child- bearing population in each year are necessary to obtain a more complete picture of the factors underlying the changing birth rates. In addition, information on the spacing of children in relation to date of marriage and date of birth of the previous child would permit an evaluation of the effects of changes in the timing of birthsin terms of both period and cohort fertility measures, In-