What caused certain European countries to have a great % of nobility in society, while in other countries nobility was much more aristocratic?

by BigBad-Wolf

Estimates of the % of nobles in the Polish-Lithuanian Commonwealth that I've seen range from 5% to 15%, with many of them not being landowners. At the same time, the aristocracy of France constituted 1% of society during the French Revolution, and I've heard that Sweden and Germany had even fewer nobles. Why was that?

This_guy_flies

it would be useful if you could provide some sources for those numbers.