In economically developed countries, aging societies with fewer children are progressing. Increased longevity has necessitated postponement of the working retirement age. Our paper presents an examination of how subsidies for an elderly labor supply and a decrease in the population growth rate affect the elderly labor supply and intergenerational wage inequality between younger people and elderly people. Our paper presents the derivation that this subsidy raises the elderly labor supply. Based on the contribution rate for pension and the elasticity of substitution between young labor and elderly labor, the effects of a decrease in population growth on the elderly labor supply are ascertained. Moreover, the study described in this paper derives the positive subsidy rate for elderly labor to maximize social welfare.