Long-term Trends of Number of Children Born to Japanese Women and Age-Specic Fertility Rates

Abstract

Childbirth occurs at a certain stage in life, mainly between the late teens and 40s. The trend of this life event from the distant past may be linked to subsequent changes in lifestyle and health, and may be related to mortality and other outcomes. It is important to take into account the year of birth rather than just the calendar year. Therefore, we estimate the long-term trends in the number of children born to Japanese women according to year of birth. Using the number of children born to wives aged mainly 45–49 from the population census and the national fertility surveys during 1950 and 2021, we obtained the distribution of the number of children born to Japanese women, born between 1890 and 1973, adjusted by the female unmarried rate. Since this distribution of the number of children born is calculated at ve-year intervals, we further conrmed the detailed changes by age-specic fertility rate at one-year intervals.