First of all, this chapter examines where and how many poor people reside in the world and whether and to what extent the number of poor people has been declining. Then, we examine the causes of poverty, such as the dependency ratio resulting from high population growth and low labor income, through an international comparison. After discovering the significant gap in labor income among countries, we examine the differences in occupational structure, labor productivity, and the incidence of poverty between low-income and high-income countries. Finally, we analyze how poverty is related to income distribution.