my guess is that legacies are just a good proxy for donations in general. if someone encourages their child to apply to the same college they attended, they pro

my guess is that legacies are just a good proxy for donations in general. if someone encourages their child to apply to the same college they attended, they probably feel more connected to the institution than the average graduate (and have donated more accordingly). legacy admissions policies may also encourage people to donate more because they know their children will have a better chance of benefiting from the investment. it's likely a decent proxy for wealth, too; someone who graduated from an elite institution is probably well above the median income. so basically it correlates with a lot of things that the institution wants, but doesn't want to state as an explicit policy.