What else are they going to do with the money but invest it? Even if they let it sit in a relatively conservative investment, a bank is still probably going to be investing their money. In my opinion, the more important impact of higher taxes on investors is what that does to the total pool of investment money over time, since they are likely to reinvest a lot of their earnings. But that is also the exact thing a progressive tax system is meant to do -- shrink their wealth and redistribute it to others.