[geezer]

I agree with the point that traders can easily quantify their value, but there is a more fundamental reason at play here. First, trading is a very scalable profession. The more you can bet, the more you can win (or lose). The fact is that how much a trader can bet has been increasing in leaps and bounds, especially during the last 30 years. That's owed partly to changing structure of the global economy and partly to changes in rules and regulation.

Consider, for example, the the repeal of Glass-Steagall act. Just by repeal of this one regulation, the bankers were able to bet many times more money, dramatically increasing short-term profits at the expense of making the system more fragile.