The analysis to detect changes of unequal opportunity in social mobility: An application of binary logistic regression model

This paper presents the method which uses binary logistic regression model to estimate the degree and its changes of unequal opportunity in intergenerational mobility. In this model, the time variables, the dummy variable of father's class which denotes the same category to the dependent variable on son's class, and the interaction variables are employed as independent variables. The parameter estimated by this model parallels to observed log odds ratio in a mobility table and reflects changes of unequal opportunity caused by time period, birth cohort and aging. The results of analysis applied to SSM survey data show that unequal opportunity in three of six classes decreased with aging, and in one class diminished with surveyed time points, while other two classes had no temporal change. The index calculated from the parameters, to measure total inequality which a society has as a whole, suggests that mobility in Japan was equalized drastically from 1955 to 1965, and gradually with transition of cohorts since 1965.