The Areal Distribution of Ageing Phenomenon in the City: For Each of the Central Cities in the Six Prefectures of Tohoku Region

Recently, the ratio of elderly (65 years old and over) is increasing rapidly in Japan. In Japan, there are some examples of studies that have examined the ageing phenomenon, however, it is very hard to find studies conducted from the view point of geography. Therefore, it can be assumed that the Japanese studies. on the ageing phenomenon have weaknesses concerning spatial or regional considerations.The purpose of this article is to make clear the areal distribution of the ageing phenomenon in the city and its promotive elements. In this study, the author fucuses on the increase of the ratio of elderly by out-migration of non-elderly from the districts. All analysis in this article is done at the scale of the census tract in several cities, for 1970, 1975 and 1980. The reason for this is that the current Japanese census tracts have been established since the population census in 1970.The methodology and results of this article are summarized as follows:First, the census tracts that have a relatively high ratio of elderly from 1970 to 1980 are obtained by using the mean and the standard deviation of the ratio of elderly. These census tracts are called Aged Population Special Districts, and are classified into three types, and their areal distributions are mapped. In the case of Sendai City as a regional central city, Aged Population Special Districts (APSD's) have distribution only in the central area of the city. However, in the case of the other five cities, they are distributed in the central area of the city and in the urban periphery.Second, the census tracts that show a remarkable decrease in population (from 1970 to 1975, and from 1975 to 1980) are obtained by using the mean and the standard deviation of the index of the increase in population. These census tracts are named Special Districts of Decreasing Population. These areal distributions are overlain on to the same maps as for the APSD's in the respective cities. In the case of Sendai City, Special Districts of Decreasing Population (SDDP's) have a more restricted distribution than the APSD's in the central area of the city. In the case of the other five cities, the SDDP's have a wider distribution than the APSD's in the central area of the city, but a more restricted distribution than APSD's in the urban periphery. Judging from the differences of areal distribution between the APSD's and the SDDP's, we can be predict the differences in the causative elements of ageing between the central area of the city and in the urban fringe.To verify these predictions, cohort analysis was carried out in the respective cities: in the central area of the city, in the urban fringe, and in other areas of the city. Judging from the results of the analysis, especially in the central area of the city, outmigration of non-elderly from the district is the main cause of ageing, and in the urban fringe, an absolte increase in the ageing population is the main cause of ageing, added to the out-migration of non-elderly from the district.All of upper results are made into a final figure at the conclusion of this article.