The purpose of the present paper is to evaluate the influence of economic level of origin and destination on migration by an unconstrained gravity model (formula 2). The data are gross inter-prefectural migration figures of the year 1955. Personal income is used as a proxy for regional economic level.
Unfortunately, statistical data for migration are affected by the size of statistical regions. Here, statistical data are standardized by formula 3. But, the standardized data (similar to rate of migration) are not equivalent in terms of their representation because the size of origin and destination for each sample is not the same. Here, the number of samples is also corrected according to the size of origin and destination by formula 5 and 6.
First, the whole migration flow is analyzed and it is found that income of both destination and origin have a positive effect on migration (table 1). Thus we can believe that in 1955, higher income at the origin promoted the mobility of migration while the higher income at the destination has attracted migration. But the impact of income at destination was more important than that at origin.
Secondly, inter-prefectural migration is divided into four kinds by metropolitan types, i. e., from non-metropolitan to metropolitan, from metropolitan to non-metropolitan, within metropolitan and within non-metropolitan regions. Each kind of migration is analyzed and the following main findings were obtained (table 2): The migration from non-metropolitan to metropolitan is mainly dependent on the income at the destination while the contrary migration from metropolitan to non-metropolitan is affected mainly by income at origin.
Thirdly, the same analysis was made on 15 kinds of migration classified by income difference between origin and destination. Except for two groups, destination income elasticity changes from minus to plus in increasing trend while origin income elasticity from plus to minus in decreasing trend when income difference changes from minus to plus (table 3). We can also find that for those migrating from lower income regions to higher income regions, the destination income is the leading factor, while for those migrating from higher income regions to lower, the origin income becomes the main factor. Moreover, for those migrating between the same level regions the destination and origin income would play almost the same role.
Finally, the in- and out-migration for each of 46 prefectures are analyzed by a modified model (formula 8 and 12) and it is found that destination income elasticity for out-migration of one specified origin is negatively related to income of that specified origin. When income level of that specified origin reaches 110, 000 yen, the influence of income at destination becomes zero. Thus, the out-migration would be expected to become even. Similar results could also be found for in-migration (table 4).
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