This has been quite widely studied, actually. Many papers conclude that it’s a mix of causation, there is (unsurprisingly) some amount of actual learning of skills in college, and also (unsurprisingly) some amount of credentialism in the job market.
What does it matter though? Parent was presuming to argue from a students’ perspective. The amount of relative causation might be pretty irrelevant to a student who just wants to know what do to to maximize their chances of having a decent career. From a student’s perspective, lack of causation might even be a stronger reason than otherwise, it potentially means they can enjoy a more lucrative career with less work.
No, the main question is are the highest paid workers getting that because of college, or did the most driven and smartest go to college, and would have been equally successful had no one gone to college?
Back in the day (pre-WW2) most successful people did no go to college. College was for wealthy trust fund kids to spend some time meeting other wealthy trust fund kids, because there just weren't all that many colleges nor any need to go.
That whole college==more money thing didn't start until after WW2.
Yes, that is precisely the question that has been asked & answered, and the general consensus in the academic literature (for example https://www.nber.org/papers/w7322) is that it’s both.
The Fed paper I linked to here https://news.ycombinator.com/item?id=35212497 shows dramatically higher income and wealth premiums for educated people in the 30s and 40s, so you might want to take a peek.
This and other papers are trying as best they can to answer exactly that question, of what if there was no college. Since the hypothetical universe where college never existed doesn’t exist, they have to resort to careful scientific techniques that attempt to factor out every bias we can think of. They’re working with what they have. Papers have, for example, studied the family history of college attendance and adjusted (discounted) for when parents and grandparents attend, they have adjusted for family wealth, for race, for geographic location, for country, for tuition, etc. etc.. You can either accept that they’ve tried rather hard and come up with a reasonable answer, or accept that the question you’re demanding be answered in the specific way you want it answered is not answerable that way, your choice.
Again, I have to ask (since it hasn’t yet been answered yet in this thread) why does this hypothetical question matter from a student’s perspective? Students are deciding what to do in the world that exists now, not in a world where people don’t go to college. All they know is that outcomes are better with a degree that without, on average. If you were choosing college right now, why does it matter what happens in the alternate reality? Don’t you just think about the jobs you want in the future, what you’re interests are and how much money you want to make, and then go or not?
This and other papers are trying as best they can to answer exactly that question, of what if there was no college.
No they don't.
why does this hypothetical question matter from a student’s perspective?"
It doesn't matter from a prospective student's perspective. If someone cares only about their own success (or their children's), it doesn't matter. But it matters for society overall, so it is still worth discussing.
The first name on the study was a Wash U professor for over 25 years. The 2nd name has so far spent a significant amount of her life in academia. Only the 3rd author appears to have spent most of his career in public service.
What does it matter though? Parent was presuming to argue from a students’ perspective. The amount of relative causation might be pretty irrelevant to a student who just wants to know what do to to maximize their chances of having a decent career. From a student’s perspective, lack of causation might even be a stronger reason than otherwise, it potentially means they can enjoy a more lucrative career with less work.