The National Institute of Population and Social Security Research, which is part of the Ministry of Health, Labor and Welfare, releases population projections every five years. The figures are used by the central and local governments when formulating administrative policies. The data is important to the public pension program because it is used as the basis for estimating benefits and premiums. The institute makes projections based on low, medium and high birthrates, with the government actually using the medium figure. The Social Security Council, an advisory panel to the ministry, determines the factors used to calculate birthrates. In the past, the panel was criticized for its overly optimistic weightings of some factors, as actual birthrates have generally declined more than projected.

a computation of future changes in population numbers based on assumptions about future trends in fertility, mortality, and migration

a forecast of future population size and age-sex structure based on assumptions about the future trend of fertility, mortality, and international migration