From http://en.wikipedia.org/wiki/Social_mobility:
Research on American mobility published in 2006 and based on collecting data on the economic mobility of families across generations looked at the probability of reaching a particular income-distribution with regard to where their parents were ranked. The study found that 42 percent of those whose parents were in the bottom quintile ended up in the bottom quintile themselves, 23 percent of them ended in the second quintile, 19 percent in the middle quintile, 11 percent in the fourth quintile and 6 percent in the top quintile.
(Now, it's possible that “ability in managing wealth” is heritable to some extent, but it seems unlikely that that alone would cause such an effect, without your parents being wealthy ‘directly’ causing you to be wealthy. And note that that study was across one country -- if they took quintiles worldwide I'd expect the results to be even more dramatic.)
Heritability in ability to manage wealth would explain this, actually. Assuming it's as likely to go down as it is to go up in any given generation, and assuming a lower bound on this ability, and assuming some percentage of people are already at that lower bound and their descendants can only improve, you'd expect something like this distribution.
Not to say it -does- explain this. I don't disagree that wealth is a factor. Where I disagree is in naming it as the most important factor.
In line with the results of the poll here, a thread for discussing politics. Incidentally, folks, I think downvoting the option you disagree with in a poll is generally considered poor form.
1.) Top-level comments should introduce arguments; responses should be responses to those arguments.
2.) Upvote and downvote based on whether or not you find an argument convincing in the context in which it was raised. This means if it's a good argument against the argument it is responding to, not whether or not there's a good/obvious counterargument to it; if you have a good counterargument, raise it. If it's a convincing argument, and the counterargument is also convincing, upvote both. If both arguments are unconvincing, downvote both.
3.) A single argument per comment would be ideal; as MixedNuts points out here, it's otherwise hard to distinguish between one good and one bad argument, which makes the upvoting/downvoting difficult to evaluate.
4.) In general try to avoid color politics; try to discuss political issues, rather than political parties, wherever possible.
If anybody thinks the rules should be dropped here, now that we're no longer conducting a test - I already dropped the upvoting/downvoting limits I tried, unsuccessfully, to put in - let me know. The first rule is the only one I think is strictly necessary.
Debiasing attempt: If you haven't yet read Politics is the Mindkiller, you should.