Let's presume that eventually the top tax rate will again reach 50%... just for argument sake. Again, for argument sake, let's say Joe... or Jim... the Plumber works the equivalent of two jobs... 16 hours a day. And, of course for argument's sake, let's say that Joe's effort earns him enough money to be taxed at the 50% rate.
What should Joe do? He could give up working so many hours so that he earns less and is taxed less, but that's not his nature. He wants success, so he works despite the disincentive.
End of story? Of course not. There's always the moral of the story. In this case, Joe's mighty efforts allow our politicians to make sure that someone who has not prepared himself with knowledge and skills sufficient to obtain gainful employment will receive compensation for his misfortune... minus the government's cut... of course. That is Joe's just reward for being so productive.
All we need to do is find more Joes...