Population Change in Yonakuni-Island

Abstract

We have observed the population changes in Yonakuni-Island which is located in the southwestern most of Ryukyu-Islands. The following results are obtained. The process of population change in Yonakuni-Island is classified into several phases. They are an increasing phase before 1926, a stagnant phase from 1926 to 1944, a rapidly increasing phase immediately after the World War II, and a decreasing phase from 1950 till now. The last phase is divided into two substages at 1960. In the first substage the population decrease is mainly caused by emmigrants i.e. social factor and in the second substage it is mainly caused by reduction of natural growth rate. We can also see extreme changes in composition of population in Yonakuni-Island after 1955. They are a reduction of ratio of younger population aged 14 and less to producing population aged 15 - 64, and a rising of ratio aged population 65 and over to producing population.