Investor dollars are not kept in a giant vault, but they are also not necessarily "being put to use the U.S. economy." If I buy $1000 of Microsoft stock, Microsoft doesn't suddenly have $1000 more to fund their projects. Some other investor gets it because he sold, and he's not necessarily putting that money to actual use either. It's all just numbers getting updated in a giant database somewhere, over and over until someone cashes out and actually spends that money to buy groceries or something. I guess some might consider those database updates and the growth itself to be "put to use" but I don't.