C. Old-age Dependency Ratio
Age-dependency ratio are the sum of two dependent population groups aged 0-14 and aged 65 years and over divided by the working age population, multiplied by 100. Working age population denotes the population aged 15-64 who have the likelihood of being in the labour force under normal circumstances. In the present discussion of population ageing, the oldage dependency ratio is particularly relevant inasmuch as this indicator roughly quantifies the demographic weight of burden that the current working age population has to bear in order to support social security and medical expenses for the elderly. Notice that according to the pay-as-you-go system of social security, the incumbent labour force is the one who supports social and medical cost for the aged. The old-age dependency ratio may mean how many old persons have to be supported by 100 persons in working age.
According to Column (7) of Table 1, the trend in the proportion of the aged to the working-age population is shown from 1868 to 1996 (See also Figure 6). Until about 1965, the ratio was relatively small, at about 8 to 9. This means that there are 11 persons or more in working age per one old person. The burden that incumbent working population has to shoulder was relatively light in those years. After 1965, however, the ratio exceeded the level of 10 and has rapidly been increasing. By 1996, the ratio reached 21 .8, that is to say, less than five persons in working age per one old person. Certainly, the burden of support becomes heavier. Column (7) of Table 2 shows the projected old-age dependency ratio for years 1995 to 2100. The figures shown here clearly indicate that the proportion of the aged to the working-age population will increase very rapidly and to a quite substantial magnitude. In the year 2000 it would become 25.3 percent, that is to say, only less than four persons in working age have to bear one aged person. By the year 2050, the ratio culminates to the level of 59.1 percent and this means that only two persons in working age have to shoulder one aged person. Remember that until 1965, 11 or more persons in working age could be compared to one person in the elderly category. Now the ratio increases more than five times. An increase in old-age dependency ratio probably most dramatizes the imminently occurring impact of population ageing.
