What should the highest income tax bracket rate be?

[Gustaf]

I think economic research tends to point to rates above 50% or so being rather pointless, in the sense that they actually lose the government revenue. The only real point of them is to make people feel better.

So I'd go for a progressive system with the highest rates somewhere around 50%.

I think the problem with continuous functions that people are proposing here might be that it becomes hard for people to understand both the policy debate on taxation and their own budget decisions. 

[Gustaf]

I think economic research tends to point to rates above 50% or so being rather pointless, in the sense that they actually lose the government revenue. The only real point of them is to make people feel better.

Actually no, the point to high marginal rates is neither raising revenue or 'making people feel better', it is to try to reduce the power of the elite.

lol. It isn't, because it doesn't. The traditional elites were a lot more powerful back in those days than they are now - largely because they have the resources to game a complicated tax code.