The paper by Barro and Lee has been around for some time, and it was recently published here. Returns to an additional year of schooling are the lowest in Latin America and Africa.
Abstract: Our panel data set on educational attainment has been updated for 146 countries from 1950 to 2010. The data are disaggregated by sex and by 5-year age intervals. We have improved the accuracy of estimation by using information from consistent census data, disaggregated by age group, along with new estimates of mortality rates and completion rates by age and education level. We compare the estimates with our previous ones (Barro and Lee, 2001) and alternative measures (Cohen and Soto, 2007). Our estimates of educational attainment provide a reasonable proxy for the stock of human capital for a broad group of countries and should be useful for a variety of empirical work.