This article is the part 2 of the study on the method for projecting households by family type. The part I was on modeling the transition process among different family types of households headed by over 35 years old, and on the method for projecting households by family type using the transition model. The part 2 focuses on the method for projecting households in the formation stage headed by under 34 years old. "Household Projections for Japan, October 1993" was calculated by the methods developed through this study.
We adopted headship rate method by marital status and family type, and the method itself is not new. The first point newly developed is that we projected the marital status by sex under 34 years old from 1995 through 2010 based on the age-specific first marriage rates of women used in "Population Projections for Japan September 1992" Through this process, Household Projections was linked with Population Projections and reflected tendency of late marriage. The second point is that we foresaw the raise of the married male headship rates based on the Hirosima's co-residence model and projected the married male headship rates by family type, especially those of married couple from the rates of married childless women based on the age-specific fertility rates of the first parity and the age-specific first marriage rates. The characteristics of this study is not extrapolating mechanically the parameters of headship rate method by marital status and family type, but rather developing the method to project them based on the marriage and fertility model and the co-residence model developed in the Institute of Population Problems.
Among projection outcomes, the proportion never married of male aged 30-34 goes up from 32.8 per cent to 37.8 per cent between 1990 and 2010, and the proportion never married of female aged 25-29 from 40.4 per cent to 47.1 per cent. Tendency of late marriage will continue to the beginning of the twenty-first century. On the other hand, the male headship rate of married couple aged 30-34 increases from 18.3 per cent in 1990 to 28.7 per cent in 2010 and this is the most remarkable change among all age groups and family types.