The wage premium on tertiary education : New estimates for 21 OECD countries This study focuses on the single most important component of the private return on tertiary education the gross wage premium. There are at least two additional reasons for paying particular attention to wage premia. First the wage premium earned by existing graduates is easy to observe so high school leavers can be assumed to take it into account when deciding for or against enrolment in tertiary education. Second to the extent that wages reflect marginal labour productivity estimates of wage premia are sometimes used to assess the quality of human capital in an economy with a view to correcting simpler measures based on years of schooling or attainment levels.