The municipality-level variables we considered were types of municipalities where the participants were born (wards; cities; towns or villages, categorical), proportion of unemployed workers over 15 years of age in each municipality (continuous), and per capita tax income in each municipality (continuous). The types of municipalities and the proportion of unemployed workers were obtained from the 2000 National Census. The area mean income was derived from dividing total taxable gain of each municipality in 2000 by the number of taxpayers in the municipality in 2000. The data were obtained from the Statistics Bureau, Japan (Statistics Bureau, 2004).