The Journal of Population Studies

Although Japan experienced a transient increase followed by sudden decrease in the reported number of HIV infections among the non-Japanese in 1991-1992, we still do not have an explanation with persuasive power for the trends of HIV infections among the non-Japanese. Our study investigated ecological associations (associations between aggregated risk factor and outcome) between reported number of HIV infections and estimated number of HIV-infected among the non-Japanese staying in Japan, focusing specifically on those originating from six selected Southeast Asian countries. Through the use of backcalculation method, the crude time-series prevalence of HIV infections in each country of our subject was estimated. Furthermore, we estimated the crude number of HIV-infected among foreign nationals from Southeast Asian countries who were staying in Japan between 1986 and 2001, and performed univariate and multivariate linear regression analyses in order to investigate ecological associations. Both the number of foreign nationals from Southeast Asian countries (adjusted R^2=0.2800) as well as the estimated number of HIV-infected among them (adjusted R^2=0.6007) could roughly predict the reported number of HIV infections in Japan. Our model suggested that the trends in the number of foreign nationals from Southeast Asian countries with the simultaneous background of ongoing HIV epidemic was the major factor that influenced the trends of the reported number of HIV infections. Other possible factors affecting the trends of the reported number of HIV infections among non-Japanese were discussed.

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All demographic data shows clearly that Okinawa is a region of longevity. When the life expectancy for men is the same as the whole Japan, the life expectancy for women shows 1.4 years more compared to mainland Japan and overpasses 86 years, a threshold that was considered two decades ago as the maximal limit for human life expectancy. As far as the prevalence of centenarians is concerned, the situation is even more exceptional as there are more than 40 living centenarians per 100.000 inhabitants while this figure is only 15 for mainland Japan. A lot of demographers have studied in detail the Japanese mortality pattern when the population of Japan became the longest longevity population world-wide. Nutrition and life style were considered by epidemiologists, gerontologists and other scientists in public health as being the most important reasons in order to explain the Japanese superiority. In this context the situation of the mortality pattern in Okinawa is still more exceptional. But already at the end of the '80, a lower improvement for the mortality risk among the young adults was identified in Okinawa. More recently, when the ranking of the male life expectancy felt from the 4th to the 26th place, the importance of this change was considered by the population of Okinawa as a "shock". Our in-depth analysis of all available life tables and associated mortality rates proves that when facing the mortality risk the population of Okinawa has to be divided into two groups of generations: these born before the WW II and these born after. The older generations clearly experience a highly favourable mortality pattern while younger generations show mortality levels that are definitively higher compared to mainland Japan. The discussion considers some factors that may explain this particular situation and the possible consequences for longevity trends in Okinawa.

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In this paper, the effect of the cost of raising children on fertility rate is estimated in order to test the hypothesis that this cost caused the recent fertility decline in Japan. Two measures of the cost of raising children were used. One measure was the cost on the Rothbarth model of equivalence scale, and the other was monthly expenditure on children (per child). Since the cost of raising children is an endogenous variable, instrument variable estimations were made. In the estimation in which the number of children is used as the dependent variable, the cost of children showed statistically significant negative effects on fertility. Thus, an implication for policy is that decreasing the cost of raising children is likely to have a positive affect on the fertility rate. Examples of such policies are extensions of the subsidies for education or medical expenses of young children.

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