An Aspect of Implications of the Increase in Expectation of Life at Birth of Japanese Males in the Period of Ten Years from 1950 to 1960

Abstract

According to life tables for the Japanese prepared by the Institute of Population Problems, Japan, the expectation of life at birth of males increased by 7.47 years from 57.90 years in 1950 to 65.33 years in 1960. The author has examined to what extent the changes in the life table mortality of various age groups of the Japanese males in the ten years contributed to the increase in the expectation of lif e at birth. The following two ways of analysis were adopted:1. Assuming the mortality under x years of age changes from the level of 1950 to that of 1960 and the mortality of x years of age and over remains at the level of 1950, the degree of contribution of such change in mortality pattern was computed. The results summarized in Table 1 on p. 167.2. Assuming the mortality of x to x+5 years of age group alone changes to the level of 1960 and the other parts of age had the same level of mortality as that of 1950, the degree of contribution of such change in mortality patten was computed. The results are shown in Table 2 on p. 170.Finding : Column (5) of Table 1 shows the additional contribution of the change in mortality of x to x+4 years of age group to the increase in the expectation of life at birth when the mortality of under x years of age has already changed to the level of 1960 from that of 1950. Column (6) of the same table shows such additional contribution in the form of percentage.Column (4) of Table 2 indicates values of contribution in years derived from the computations following the second analyzing method. These values may be called independent contribution of each age group.The decline in mortarity of under 4 year of age from 1950 to 1960 alone was found to have a potential to increase the expectation of life at birth by 31.3 years from the level of 1950. This corresponds to 42.13% of the total increase of the expectation of life at birth during 1950 and 1960. Assuming the mortality of under 45 years of age declines to the level of 1960 and those of the higher age groups remain at the level of 1950, such change in mortality pattern contributes to the increase in the expectation of life at birth by 80.88%. Among values of independent contribution of the mortality change of each five-year age group shown in column (4) of Table 2, the value of the age group 20-24 years takes the second place next to the age group 0-4 years and it has a potential to increase the expectation of life at birth by 0.59 year from the level of 1950.