Acemoglu, Johnson, Robinson, and Yared (2008) demonstrate that estimation of the standard adjustment model with country-fixed and time-fixed effects removes the statistical significance of income as a causal factor of democracy. We argue that their empirical approach must produce insignificant...

Based on Baumol’s cost-disease model, we develop two alternative measures of the change in the productivity of schooling. Both productivity measures are based on changes in the relative price of schooling. We find that in most OECD countries the price of schooling has increased faster in...