Kids who got got good genes from their parents are more likely to go to college. And the parents who gave the kids good genes are likely to have high income.
Genetics is the most important ingredient here.
"Genetics is the most important ingredient here." is a pretty extraordinary claim, and extraordinary claims require extraordinary evidence.
So maybe genetics is not the most important ingredient, but saying genetics is not relevant to this discussion is astounding. Smarter parents beget smarter kids -- that's not a controversial statement. IQ is heritable to a large extend. Smarter parents tend to be wealthier. (This is not true everywhere, but it is mostly true in the USA, the land of opportunity.) Smarter kids do better in college. That's not a controversial statement either.
> we find that 24% (54%) of the variance of women’s (men’s) lifetime income is due to genetic factors and that the contribution of the shared environment is negligible
The Promises and Pitfalls of Genoeconomics[2] sees similar results, coming up with 46% and 58% heritability in women and men, respectively.
There's plenty of research here. "Heritability of income" is a good search term.
[1] https://helda.helsinki.fi/bitstream/handle/10138/38881/HECER... [2] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3592970/
Dismissing as "extraordinary" any claim to which you are politically opposed is not good science. (Frankly, the Sagan quote is in itself not good science until you can get everyone to agree on what is "extraordinary".)
Meanwhile, an entirely appropriate riposte to GP would have been: ""Genetics is the most important ingredient here." is a claim, and claims require evidence."