@rysiek You have a point, but at a certain structure of wealth disparity — which, AFAICT, is common in wealthy countries right now —, setting the threshold according to a median rather than average means, a zillionaire will not be rewarded for doing something that doubles, say, the revenues of one percent of the bottom-earners. And if we're stuck with trying to convince the zillionaires implement measures to support the poor people instead of doing it via a functional government, such an incentivi might actually be valuable.

All in all, I do freely admit that picking a good set of rules for taxation is more complicated than just picking something that should work. The simplistic example that I brought was meant more as an illustration of the way to probe rather than as an actual, fully formed, tax policy proposition.