Chapter Three. Statistical foundations of population projections

In December 2006, the National Institute of Population and Social Security Research in Tokyo announced a new population projection for Japan. This projection provides a sketch of expected demographic changes over a 50 year period up to 2055, with ancillary calculations of the total population up to 2105. An essential aspect of population projection is to establish assumptions on future occurrences of the vital and migratory events. The nature of these assumptions typically depends on the purpose of the projection. Fertility assumptions underlying the projection were made on the basis of the cohort-fertility method. That is, the level of completed fertility and the birth timing of each female birth cohort including cohorts whose birth process is not yet completed are statistically projected to future female birth cohorts. The Lee-Carter model is adopted as a basis to construct future annual life tables. Keywords: cohort component method; fertility rate; Japanese citizens; Lee-Carter model; population projection