>The ruling class doesn't have a big turnover in personnel , surely.
Depends on what you mean by "big" and what you mean by the "ruling class." "The rich" aren't the same as the ruling class (and since I'm about to write a book about the ruling class, I'd welcome any related discussion), but you do see considerable turnover in the Forbes 400. The old WASP elite looks largely washed up, too. At less elevated level, there is some downward mobility out of the top income quintile; according to Peter Gottschalk, just 39% of the families who were in the top quintile in 1969 were in the top in 1994. (25% were in the 4th, 17% in the 3rd, 11% in the 2nd, and 9% in the bottom.) The pattern for the bottom quintile was roughly similar (though just 6% made it into the top). Of course the top quintile is still just what we'd think of as the upper middle class - the very rich/ruling class types aren't included in surveys. But still, there's turnover.
Doug