This chapter conducts a demographic analysis of the changes in the elderly population by prefecture from 1980 to 2010 (actual) and from 2010 to 2040 (projected). Changes in the elderly population are categorized into national factors (new elderly and mortality) and regional factors (regional new elderly, mortality structure, mortality survivorship ratio, and net migration rate), and four main results are found. First, changes in the elderly population by prefecture are largely affected by national factors as a whole. Second, some prefectures are prominently affected by regional factors, and significant variations are observed between prefectures, particularly with regard to the regional new elderly and mortality structure factors. Third, the survivorship ratio and net migration rate factors have relatively low contributions among the regional factors. Although there is a certain difference in the survivorship ratio among the elderly by prefecture, the impact on changes in the elderly population is low compared with the population structure. The net migration rate of the elderly among prefectures is low, so migration also has a limited impact after one becomes an elderly person.