近年のわが国における有配偶出生力の人口学的分析

結婚年齢,結婚持続期間,および出生順位に着目して

抄録

The purpose of this study was to analyze the levels, timing and trends of marital fertility in recent Japan, in which total fertility has been below the replacement level.Using the vital statistics, marital duration-specific fertility rates, broken down by ageat marriage and birth order, for the 1980, 1985 and 1990 marriage cohorts and rates for first birth for the 1970 and 1975 marriage cohorts were estimated, and the related demographic factors were also examined. The major findings were as follows: 1. The cumulative fertility rate at 14 years after marriage, which is regarded as the completed fertility rate, for the 1980 marriage cohort was 2.02. The lower this rate the higher age of women at marriage: 2.20, 2.03, 1.56, 0.70 and 0.12 for the women who married at ages 20-24, 25-29, 30-34, 35-39 and 40-44. A comparison among the 1980, 1985 and 1990 marriage cohorts showed slight declines in fertility. 2. An analysis of the parity progression for the 1980 marriage cohort indicated that 93.6% of the couples had the first birth and 80.7% progressed to the second birth and 37.8% to the third or higher-order birth. The proportion of the women by total number of births was as follows: 6.4% childless, 18.1% one child, 47.0% two children, 28.5% three or more children. Also observed were increase in proportion of childless couples and the downward progression from the first birth to the second birth and to the third birth in the three marriage cohorts, and the delayed timing of births in the 1990 marriage cohort in particular. 3. It is suggested that biological, social and psychological factors accounted forlower fertility among the women who married at higher ages. The age-dependent suppressing effects of fertility have probably obstructed achievement of the couple's desired number of children due to delayed marital age in today's Japan. This study also highlights importance of social support for the couple's desired timing of births.