A study published by the American Enterprise Institute Wednesday suggests that the proportion of low-income students at selective colleges is edging up, not decreasing, as some other recent studies have suggested. Instead, the paper argues, the group that has been most squeezed out of selective private and public colleges in the last decade has been those students in the middle socioeconomic quartiles.

But the impression most readers of the study are likely to be left with is that students from the top quartile continue to dominate enrollments at the 200 most selective colleges and universities. In 2015-16, the latest year for which AEI had data from the Education Department's National Postsecondary Student Aid Survey, 54.2 percent of undergraduates at those colleges were from the top 25 percent of the socioeconomic ladder, while the remaining students were split fairly equally from the other three quartiles.