Abstract
This paper aims to disclose the demographic factors of change of migrants （in-migrants and out-migrants） after 1980s, with Tokyo ward area as a target. In this paper, it has been attempted to clarify the demographic mechanism of “re-centralization” by decomposing change of migrants to population structure factor and mobility factor, by applying the method of indirect standardization. Three major findings are obtained. First, the expansion of net migrants in Tokyo ward area was mainly brought by a decline of out-migration mobility at the beginning, but an increase of in-migration mobility gradually had great impact. Second, in-migration mobility of Tokyo ward area was increasing from all prefectures after mid of 1990s, while out-migration mobility of the area was decreasing to all prefectures. Although net-migration mobility increasing from prefectures in Kansai area was high, those from surrounding prefectures were relatively low. Third, population structure factor has a certain influence on both in-migrants change and out-migrants change. This suggests the possibility of net-migrants reduction of Tokyo ward area in the future. If we are to understand the change of migration tendency correctly, it would be indispensable to analyze the mobility of both in-migration and out-migration.
