[shkkmo]

I simply do not see a anything in that study that refutes that college is just a proxy for parental income. The study only discusses parental background in terms of parental education and I don't see any controlling for parental income (though those two factors are clearly correlated, but are not identical and conflate them in several places.)

In reality, a significant part of the correlation between of college and is indeed due to college being a partial proxy for parental wealth. At the same time a significant part of the correlation between parental wealth and child income is to the that same proxy.

Even when you control for parental wealth, there are large heterogeneities in the effect of college on income in different groups. This makes it hard to argue for a simple, direct causal link between college and income.

While I think you and me tend to agree on this subject, I think you should focus less on being the "thread secretary" and more on understanding the opposing argument and clearly explaining your argument rather than posting dense statistical papers with no analysis and using abstruse acronyms.