[kleiba]

You make more than your sister doing "less" work because knowledge and high level skills are a value multiplier. You may come up with a world changing idea that generates billions of dollars. No kindergarden teacher could achieve that. Pay matches accordingly.

Except this argument doesn't seem to apply globally: I have a good friend over here in Europe who's got a PhD in computer science. He works as a researcher in a renouned university. His sister is not a kindergarden, but elementary school teacher.

She makes (slightly) more money than he does. Her work day starts at 8am and most of the time ends at 2pm. She's got around 10 weeks of vacation per year. She cannot legally get fired if she performs badly.

So in this country, my friends knowledge and high level skill levels certainly weren't a value multiplier when compared to his sister.

Granted, he might be able to get a higher paid job with his background, but that brings us back to the grandparent's original point: your education is not a good predictor for your salary.