They're billionaires because of the work ethic, not necessarily their work ethic. Bezos isn't optimizing his own productivity, he optimizes his employees productivity and spends his time as he pleases. He keeps the gains from the productivity regardless.

EDIT: Actually I don't know if Bezos optimizes his own productivity or not. Nevertheless, his own productivity is a drop in the bucket compared to the thousands who work for his companies.

> They became billionaires in large part because of their work ethic.

Tell me you're an American without telling me you're an American. :)

Thomas Piketty wrote a book on this topic (which I highly recommend) called "Capital in the Twenty-First Century".

That's what they'd certainly like you to believe. The success of ycombinator depends on it!