The National Institute of Population and Social Security Research released Regional Population Projections for Japan: 2010-2040 in March 2013. The objective was to project future population by prefecture and municipality. This new round of the projection took the results of Population Census of Japan 2010 (Statistics Bureau, Ministry of Internal Affairs and Communications) as the initial population, and produced the future populations as of Octorber 1st by five-year age group and sex each five years from 2015 to 2040. Until the last round of the regional projection, we first projected prefectural population, and then municipal population. In this new round, we first projected populations by municipality, then obtained prefectural population by an aggregation over the municipalities that belonged to the prefecture concerned except Fukushima prefecture.

The geographical units that the projection covered were comprised of 1,799 municipalities (23 Tokyo special wards, 128 wards in 12 major cities*, 764 cities, 715 towns and 169 villages) by the boundaries as of March 1st of 2013 and 1 prefecture (Fukushima). The sum of populations over individual regions by age and sex reported here is consistent with the medium-variant fertility and medium-variant mortality projection results of the national projections (published in January 2011).