The changing selectivity of US colleges

In the United States, there is this general impression that it is getting harder and harder to get into college. In particular, universities crow how the average SAT scores of entering classes keep increasing cohort after cohort. How is it in reality?

Caroline Hoxby shows that this increased selectivity is only true for top colleges. Half of the colleges have become less selective. And why these changes? Students have become more mobile and strive more to get into the best colleges. They care less about local option and want the best.

Still, it is an old tradition for Americans to move afar for college. Europe is just now moving in that direction, in particular thanks to the Erasmus initiative. While the quality of tertiary education institutions is much more uniform than in the US, the increased mobility could lead to dispersion not unlike the one we see now in the United States.