In this paper I tried to show how the ageing of the population influences the change in the growth of employment, employment structure, the savings ratio, economic growth and the cost of social security. In the latter part of the paper I suggested a close correlation between the average marriadge age of woman, the total fertility rate and the work participation ratio of woman. According to the latest demograghic forecast by the Japanese Government, the proportion of the elderly (65 years old and over) to the total population will be 17% in 2000 and more than 25% in the 2020s respectively. On the other hand, the productive age population between 15 and 64 years old, which has been increasing, is forecast to decline from the middle of the 1990s. As a result, the proportion of the aged to the working population will increase markedly. The correlation between the proportion of the elderly and the social security benefits / national income ration is quite high. Simple regressions (OLS) suggest that the percentage ratio of elderly people in the working population (No/Nw in regression (1)〜(2)) is one of the main variables that explain the behaviour of the percentage ratios of social security benefits in national income as the following regressions show. [numerical formula](1) [numerical formula](2) Based on the 1960〜1991 annual data. B: Social security benefits, Y: National income, Nw: Total working population=productive age population multiplied by (1-u), No: Population of the elderly (65 years old and over), u: Unemployment ratio as a ratio of total working force, U_2: Unemployment as a ratio of employees, dw/w: Rate of increase of employees compensation per employee, Bm: Social insurance benefits for health service, D_1: Dummy variable 1960〜1973=0, 1974〜1988=1. This dummy variable explains the change in political situation since 1973. 1973 was called the "First year of welfare"., R^^-^2: Adjusted determinant coefficent, D.W.: Durbin Watson ratio, Figures in parentheses under coefficients of explainig variables are t statistics. The correlation between the work participation ratio, the average marriadge age of woman and the total fertility rate is also impressive as Fig. 9 and 10 show. However, the correlation is not inevitable as the recent experience in Sweden suggests. Active family policy based on universalism must be introduced in Japan.