Characteristic features of modern American fertility

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Citation: Morgan, S. Philip Characteristic features of modern American fertility.
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This article identifies the prominent features of contemporary U.S. fertility. These are: 1. Changes in fertility are largely period driven. In calendar years where fertility increased (decreased), it did so uniformly across all age groups. Period effects tend to be somewhat larger for women in their 20s. 2. The high age-specific rates of the Baby Boom would have produced even more births had the age structure of the population been more favorable. 3. The timing shifts that occurred during the 1960s-1970s were roughly comparable in magnitude to those experienced during the Great Depression of the 1930s, but the downward pressure on period fertility exerted by this timing shift seems to have run its course and period fertility rates have been relatively stable since 1975. 4. Timing and occurrence of first and second births are the key components determining current levels and future trends in fertility. Currently, roughly 75% of the fertility rate results from women's first and second births. Despite this, fertility has not become more concentrated by age. 5. Increased fertility among women in their 30s. The 1932 cohort shows large proportions had first births in their teens and early 20s. The 1954 cohort is characterized by delayed fertility larger proportions had first births in their 30s. In 1993, women in their 30s contributed 28% of the TFR. The proportion of the TFR contributed by women in their 40s has always been small and has declined in the recent period. 6. Persistent high levels of teenage childbearing. Teen childbearing accounts for 15% of the fertility rate in 1993. Teenage childbearing has remained stable across time, with a possible upturn in the most recent data. Age at first intercourse has declined for both males and females. Early intercourse is more common among blacks, those whose mother has less education and those not living with both parents at age 14. Controls on socioeconomic status do not eliminate racial differences. Sexually experienced teens on average have had sex in only 8 of the past 12 months. 7. Slowed pace of transition from second to third births for women in all age groups. Early in the twentieth century, fourth and higher order births accounted for more than 40% of the fertility rate. By 1991, women at these high parities contributed only 10% of the fertility rate. 8. Substantial proportions of women will remain childless. Delayed childbearing is becoming a more visible feature of the modern American fertility pattern, and this trend has not run its full course. 9. A substantial proportion of births will be to unmarried women. 10. There have been modest fertility rate convergence between non-Hispanic whites, Hispanic whites, and Asians, but differentials between non-Hispanic whites and African-Americans are expected to remain substantial. 11. Contraceptive use, contraceptive failure, and abortion are key proximate determinants of fertility for all age groups. a. Low contraceptive use appears to be responsible for the high rates of teenage childbearing that U.S. experiences relative to other countries, possibly because U.S. teens find it difficult to obtain contraceptives. Contraceptive use has increased during the 1980s, with about 2/3 of teenagers using some form of birth control (most commonly condoms). Contraceptive failure rates are estimated at 26% for teens and 13% for women ages 25-29. Sterilization and pills are the most commonly used. b. In 1990, 35% of teen pregnancies ended in abortion. Declining abortion rates account for part of the increase in teenage fertility observed in recent years. Abortion rates appear to have declined since the early 1980s.