Development of Model Life Tables for Japan and Their Application for Estimation of Regional Life Tables: Based on Modification of Flexible Model

Abstract

In this study, we attempt to develop a mortality model that reflects the improvements in the mortality rate of Japan’s elderly since 1970, using the Japanese Mortality Database （JMD） life tables organized according to prefecture.

Specifically, we first apply the Flexible Two-dimensional Model （Flexible Model） by Wilmoth et al. （2012） to the JMD life tables per prefecture. We use the coefficients of the Flexible Model, which are derived from 719 life tables in the Human Mortality Database （2021）. As a result, it is confirmed that the estimation error of the Flexible Model becomes larger particularly in the elderly age group of 65 years and older, and that the estimation error tends to increase as the life expectancy at age 65 increases.

Based on these observations, the estimation errors of the Flexible Model in the age group of 50 years and above are stored in the form of a matrix, and we apply Singular Value Decomposition to the matrix. Then, we derive the first singular value and the corresponding left and right singular vectors and fix the product of the first singular value and the left singular vector as coefficient of the proposed model （Modified Model） for the usage of indirect estimations. This Modified Model is also compared with Clark’ s （2019a） model.

Finally, the Modified Model proposed in this study is applied to the Japanese Ministry of Health, Labour and Welfare's Municipal Life Tables from 2015, and it is confirmed that the mortality rate can be estimated accurately. Therefore, it is suggested that the Modified Model can be applied to future population projection at the municipal level.