The entire debate in congress over taxes is that President Obama wants to restore the top marginal rate to the level that Dimon thinks it already is. Meanwhile, Dimon doesn’t even know what tax rate he pays.
I think that this quote is really, really important. Classical economic models presume that individuals act to maximize their utility. But real people often have limitations, including lack of perfect information about what costs really are. I would be surprised if Mark did not have follow-up thoughts.
But the key point is that if these assumptions about informed persons can't hold for the CEO of JP Morgan Chase (whom you would assume is numerate) then how likely is that these models are going to be good at prediction? After all, we presume Jamie Dimon is maximizing his utility for a 39.6% marginal tax rate; so a change in taxes to what he currently thinks that they already are would alter his incentives how?