The adverse economic events following the First World War turned me toward economics... I learned during my youth how hard it was for farm families t… - Theodore Schultz

Although it is obvious that people acquire useful skills and knowledge, it is not obvious that these skills and knowledge are a form of capital, that this capital is in substantial part a product of deliberate investment, that it has grown in Western societies at a much faster rate than conventional (nonhuman) capital, and that this growth may well be the most distinctive feature of the economic system.

Human beings are incontestably capital from an abstract and mathematical point of view.

Much of what we call consumption constitutes investment in human capital. Direct expenditures on education, health, and internal migration to take advantage of better job opportunities are clear examples. Earnings foregone by mature students attending school and by workers acquiring on the-job training are equally clear examples.