This paper analyzes the growth of public social expenditures in Korea from a public choice perspective. Specifically, based on the median voter theory, we conduct an empirical analysis of social insurance expenditures such as national pension, national health insurance, and public social expenditures using time series data from 1993 to 2022. The empirical results support that changes in the budget constraint for lifetime utility maximization of the median voter, including financial assets, remaining life expectancy, and remaining working year, are associated with an increase in public social expenditure. In addition, macroeconomic variables such as the real interest rate, real economic growth, and the tax base per recipient are also found to affect public social expenditure. This paper suggests that as the age of the median voter increases, public social expenditures, including national pensions and national health insurance, are bound to increase both naturally and politically.