English: Predicted versus actual GDP per worker. The figure shows how much one would expect each country’s GDP to be higher based on the data on average years of schooling. The calculation is made by Weil (Weil, D. (2009) Economic Growth. Pearson Addison-Wesley.) based on data from Hall and Jones concerning the returns on education (Hall, J. & Jones, R (1999) Why Do Some Countries Produce So Much More Output per Worker than Others? Quarterly Journal of Economics 114: 83–116.). The GDPs predicted by Weil’s calculations are plotted against actual observed GDPs. The results indicate that variation in education explains some, but not all, of the variation in GDP.