Education quality is roughly as important as cross-country differences in years of schooling

Interesting. From Education Quality and Development Accounting by Todd Schoellman. From the abstract.

This paper measures the role of quality-adjusted years of schooling in accounting for cross-country output per worker differences. While data on years of schooling are readily available, data on education quality are not. I use the returns to schooling of foreign-educated immigrants in the U.S. to measure the education quality of their birth country. Immigrants from developed countries earn higher returns than do immigrants from developing countries. I show how to incorporate this measure of education quality into an otherwise standard development accounting exercise. The main result is that cross-country differences in education quality are roughly as important as cross-country differences in years of schooling in accounting for output per worker differences, raising the total contribution of education from 10% to 20% of output per worker differences.

Quality of education - an important variable that is often ignored.