[[Proportional hazards model analysis of women's reproductive career in present-day Japan]].
The 1st section of this paper, using a method to decompose a change in the total marital fertility rate into the quantum and tempo effects, confirmed the major effect of birth timing on the 1970s trends in the total marital fertility rate based on the pooled data of the 8th and 9th Japanese National Fertility Surveys of 1982 and 1987, respectively.  In the next section, proportional hazards model analyses of the 1st, 2nd, and 3rd birth functions for the pooled data made it clear that the 1st and 2nd birth intervals among the marriage cohorts since the end of the 1960s were shorter than those in the early 1960s even after having controlled for other variables.  Given that 1 conception or more can occur during a birth interval, proportional hazards model analyses were again utilized to examine the effects of various variables on the time elapsed since marriage and the 1st conception, the time between the end of the 1st pregnancy and the 2nd conception, and the time between the end of the 2nd pregnancy and the 3rd conception.  The authors found that the 1st-conception probability of the marriage cohorts since the late 1960s was smaller than that of predecessors, while the 2nd-conception probability was not affected by marriage cohort.  In the last section, a logistic regression analysis of the probability of induced abortion showed that the probability of aborting a 2nd pregnancy decreased in the 1970s compared with that in the early 1960s.  When a proportional hazards model analysis of the 2nd birth function was applied after omitting those cases where the 1st pregnancy did not result in birth and/or the 2nd pregnancy was aborted, the strong effect of marriage cohort on the 2nd birth probability was substantially diluted.  These facts suggest that the shortened 2nd birth interval in the 1970s was partly caused by the shrinking probability of aborting a 2nd pregnancy in this period.
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D000028:Abortion, Induced; D001208:Asia; D001721:Birth Intervals; D001723:Birth Rate; D015331:Cohort Studies; D003710:Demography; D019049:Developed Countries; D005193:Family Planning Services; D005202:Asia, Eastern; D005298:Fertility; D007564:Japan; D008393:Marriage; D008962:Models, Theoretical; D011153:Population; D011157:Population Dynamics; D011336:Probability; D012106:Research; D013223:Statistics as Topic; D013997:Time Factors
Abortion, Induced; Asia; Birth Intervals; Birth Rate; Cohort Analysis; Demographic Factors; Developed Countries; Eastern Asia; Family Planning; Fertility; Fertility Control, Postconception; Fertility Measurements; Fertility Rate; Fertility Surveys; First Birth Intervals; Japan; Marriage; Models, Theoretical; Nuptiality; Population; Population Dynamics; Probability; Research Methodology; Statistical Studies; Studies; Time Factors; Total Fertility Rate