This chapter focuses on schooling, as an investment with market returns is not intended to detract from the importance of education as a public good and as a source of consumption benefits, but rather to review how economic concepts and statistical methods have recently progressed in quantifying the roles of education in economic development. This chapter surveys a small part of the extensive literature on the linkages among education, productivity, and development, and assesses several areas where concerted research might clarify important issues and potentially change policies. This chapter presents an economic interpretation of this educational explosion. Most of the growth in public expenditures on education is attributed to increases in growth of real income per adult. The chapter describes the expansion of the world's educational system both in terms of its inputs of public and private resources and its output of students, and then estimates how income, price, and population constraints appear to govern this process. The chapter presents a contrast on causal frameworks proposed to explain the relationship between education and productivity, and discusses sources of data to measure the relationship and discriminate among causal interpretations. The chapter reviews evidence on the market returns to schooling measured for entrepreneurs and employees, men and women, and migrants and nonmigrants. The chapter also presents the evidence of schooling's effects on nonmarket production. The chapter discusses the policy issues for development that arise from the apparent effects of education on economic productivity and the mechanisms used to finance and manage the educational system.