[randomdata]

> If you broke it into quartiles i bet the top quartile college graduate does much better than the top quartile plumber.

Yes, as long as college here means that one has a professional degree (MD, JD, etc.), where access is granted to a career with an artificially constrained labour supply, thereby producing artificially high incomes. Of course, it's the supply management that boosts incomes, not some mystical power of the degree itself.

Interestingly, having only a bachelor degree seems to put you in a worse position than without, based on what we see in the makeup of high income earners. Which probably isn't too surprising. Graduating from college, save striving for a professional degree to gain access to an artificial market, is where you end up if you weren't already found to be useful in the economy. It's a sign of someone failing economically.