This dissertation studies the impacts of public assistance and social insurance policies on vulnerable populations. Chapter 1 investigates the effects of the Universal Lunch Program on students' academic achievement in South Korea and its implications on households' educational investment decisions. Chapter 2 examines the labor supply and consumption response to cash assistance by studying the Temporary Assistance to Needy Families (TANF) in the US. Chapter 3 investigates how public old-age pension receipt affects labor supply and health by focusing on the pension reform in South Korea.