I haven’t been able to find any raw statistics on this, so I can’t confirm my suspicions, but it seems to me that the incentives are very different for the rich than the merely well off. Most income variability in the US lies within the top tax bracket rather than between brackets, so studies which lump together everyone in, say, a $250,000+ annual income bracket may disguise variability above this level.
I haven’t been able to find any raw statistics on this, so I can’t confirm my suspicions, but it seems to me that the incentives are very different for the rich than the merely well off. Most income variability in the US lies within the top tax bracket rather than between brackets, so studies which lump together everyone in, say, a $250,000+ annual income bracket may disguise variability above this level.