Additionally, I've found that the smartest people who go to prestigious schools care more about prestige and interesting work than about salary. The best CS and math students at Harvard wanted to be professors or do research. It was the average Harvard students, for the most part, that went to finance or consulting to make the big bucks.
PG made a point (I think in one of his essays that I can't remember - correct me if I am wrong) that I've found to be fairly true (though of course not always) - that often, jobs for a given level of qualification have a set wealth they will pay, and this payout can come in the form of a more interesting job or more money. This generalization does have a subtlety though - when you are a higher valued candidate for work, you are not only offered more wealth but a greater diversity of choices of work that offer different proportions of interest vs. money. Essentially what I mean here is that it is much easier, coming out of Harvard, to get a high paying job than it is to get a really interesting job. When you are in the middle rungs of math at Harvard, it is not that hard to get a job as an I-banker (lots of money, but two years of very boring work), but you can't just trade off some of that money for a more interesting job. It is only when you are smarter that you get the option of having either the high paying I-banking job or a lower paying job that is more interesting (i.e. cutting edge grad school work at MIT's AI lab). A lot of the smartest people want this more interesting job not only because they are driven more by their interests than money, but also because these jobs are more prestigious since only the smartest people can have them.
On top of this, I knew a lot more people from Harvard who were willing to forgo making much money in their earlier life by taking travel grants or just going off to some country to make some documentary or doing a startup (something that I think has a much lower total expected outcome of income than a finance job). A lot of the smarter people were willing to sacrifice money for freedom because they were sure they would probably eventually make enough money to survive (and the degree helped this), and freedom was just more important to them.
Given all this, measuring money in these studies doesn't even seem good enough to me to be a heuristic for success. People at the most prestigious universities seem to often have the freedom and luxury to have different priorities and to simply not care as much about money. It seems like even a study asking people about their job satisfaction some number of years later would be better.
PG made a point (I think in one of his essays that I can't remember - correct me if I am wrong) that I've found to be fairly true (though of course not always) - that often, jobs for a given level of qualification have a set wealth they will pay, and this payout can come in the form of a more interesting job or more money. This generalization does have a subtlety though - when you are a higher valued candidate for work, you are not only offered more wealth but a greater diversity of choices of work that offer different proportions of interest vs. money. Essentially what I mean here is that it is much easier, coming out of Harvard, to get a high paying job than it is to get a really interesting job. When you are in the middle rungs of math at Harvard, it is not that hard to get a job as an I-banker (lots of money, but two years of very boring work), but you can't just trade off some of that money for a more interesting job. It is only when you are smarter that you get the option of having either the high paying I-banking job or a lower paying job that is more interesting (i.e. cutting edge grad school work at MIT's AI lab). A lot of the smartest people want this more interesting job not only because they are driven more by their interests than money, but also because these jobs are more prestigious since only the smartest people can have them.
On top of this, I knew a lot more people from Harvard who were willing to forgo making much money in their earlier life by taking travel grants or just going off to some country to make some documentary or doing a startup (something that I think has a much lower total expected outcome of income than a finance job). A lot of the smarter people were willing to sacrifice money for freedom because they were sure they would probably eventually make enough money to survive (and the degree helped this), and freedom was just more important to them.
Given all this, measuring money in these studies doesn't even seem good enough to me to be a heuristic for success. People at the most prestigious universities seem to often have the freedom and luxury to have different priorities and to simply not care as much about money. It seems like even a study asking people about their job satisfaction some number of years later would be better.