Moltissimo, almeno secondo il nuovo dataset di Barro:
Empirical investigations of the role of human capital require accurate measures across countries and over time. This column describes a new dataset on educational attainment for 146 countries at 5-year intervals from 1950 to 2010. The new data, freely available online, use more information and better methodology than existing datasets. Among the many new results is that the rate of return to an additional year of schooling on output is quite high – ranging from 5% to 12%.