The second in a series on "Six big ideas" in economics at The Economist.
"As far back as Adam Smith in the 18th century, economists had noted that production depended not just on equipment or land but also on peoples’ abilities. But before the 1950s, when Becker first examined links between education and incomes, little thought was given to how such abilities fit with economic theory or public policy.
"Doctoral degree in hand, Becker, then in his mid-20s, was hired by the National Bureau of Economic Research to work on a project calculating returns on schooling. What seemed a simple question led him to realise that no one had yet fleshed out the concept of human capital. In subsequent years he developed it into a full-fledged theory that could be applied to any number of questions and, soon enough, to issues previously seen as outside the realm of economics, from marriage to fertility."