Comprehensive Study of Future Life Expectancy in Japan

1988 Fiscal Year Final Research Report Summary

• Project/Area Number: 61490031
• Research Category: Grant-in-Aid for General Scientific Research (B)
• Allocation Type: Single-year Grants
• Research Field: 広領域
• Research Institution: Nihon University
• Principal Investigator: KOBAYASHI Kazumasa Professor, Nihon University Population Research Institute, 人口研究所, 教授 (10167405)
• Co-Investigator(Kenkyū-buntansha): KURODA Toshio Part-time Lecturer, College of Economics, Nihon University, 経済学部, 嘱託 (80102440) ; OGAWA Naohiro Professor, College of Economics, Nihon University, 経済学部, 教授 (20139075) ; NANJO Zenji Professor, Fukushima Medical College, 教授 (10045594)
• Project Period (FY): 1986 – 1988
• Keywords: life table / life expectancy / cohort mortality / generational life table / infant mortality / model life table / rational model / 将来寿命の予測

Research Abstract

The period 1971-79 was the longest in recent years as a period without an influenza outbreak. It was this period when, along with Iceland, Japan came to have the world longest life expectancy. Especially during 1974-79, Japan's life expectancy increased significantly and steadily. Compared with this rapid improvement, however, the rate of increase during the 1980s was considerably slower. These differences in the pattern of life expectancy changes seem to be due partly to longevity decreases in 1980 and 1983 in which influenza prevailed.
When we examine the age pattern and sex differentials of the mortality changes during the 1970s and the 1980s respectively, however, we see a complex mechanism that produced these changes. One way to untangle this complexity is to analyze these "period" mortality changes in terms of "cohort" mortality changes. Specifically, we first construct the complete life tables for males and females for the period 1891-1986 (96 years), and using the estimated proportions dying, we then construct the life tables for the birth cohorst 1816-1974. Based upon these cohort (generational) life tables, we analyze cohort mortality changes. Our findings are summarized that although the pace of improvement in life expectancy slowed down in the 1980s, many of the cohorts show the trend of stabilization or even recovery in their life expectancy in recent years. These trends of stabilization and recovery are significant for projection of the future changes in life expectancy. Furthermore, since decreases in infant mortality are the most influential component for improvement of life expectancy, we also construct the model life table during infancy with the relational model, indicating suefulness of the model for analyses of period changes in infant mortality. it is necessary to further accumulate detailed demographic avidence for projection of future life expectancy in Japan.