2016 Volume 125 Issue 4 Pages 457-474
Population changes of old municipalities in the Tohoku region and the Chugoku region around the period of the “Heisei municipal mergers” are examined by decomposing population change into natural increase and social increase. Population changes during the period 1980–2010 are analyzed in two areas affected, one of which retained administrative and public offices (“Central Area”) and the other of which did not (“Periphery Area”). The results of the analysis are summarized as follows. The main demographical factor in the widening gap of the population increase rates of the “Central Area” and the “Periphery Area” from the 1980s was the widening gap in natural increase rates, as was the case throughout Japan. On the other hand, the impacts of social increase rate changes were generally limited, and differences in the social increase rates of the “Central Area” and the “Periphery Area” in the 2000s were almost the same as, or smaller than, those in the 1980s. Whereas the social increase rates of the “Central Area” and the “Periphery Area” declined in the Tohoku region, there was no such tendency in the Chugoku region. Because the social increase rates of non-merged municipalities were almost the same as those of the “Central Area” and the “Periphery Area” in both regions, the changes in the social increase rates of the “Central Area” and the “Periphery Area” after the 2000s in both regions are presumed to be a phenomenon commonly observed in both regions. When social increase rate is classified by the ratio of population of the “Periphery Area” to that of the “Central Area,” the social increase rates of the “Central Area” and the “Periphery Area” declined, regardless of the ratio in the Tohoku region, but there is no such clear tendency in the Chugoku region. However, it is observed in both regions that social increase rates largely declined in both the “Central Area” and the “Periphery Area,” which had similar populations each other. This suggests the possibility that migration from municipalities with small populations to those with large populations increased after the 2000s. When the social increase rate of the “Periphery Area” is classified by distance between new public offices and old public offices, there is a clear negative relationship between social increase rate and distance in the Tohoku region, but the negative relationship is very weak in the Chugoku region. On the other hand, there is a clear negative relationship between natural increase rate and distance in both regions, suggesting that the impact of the natural decrease became stronger in areas far from the new public office. Overall, the changes in the social increase rates of the “Central Area” and the “Periphery Area” in both regions after the 2000s reflect the migration tendency of the whole region, and the influence of the “Heisei municipal mergers” on migration is estimated to be limited compared to the effects on the entire region.
