[csense]

Much has been made of inequality recently. If a rich person makes N times as much a poor person but doesn't consume N times as much, they'll tend to park their excess income in financial assets. So if money's trickling up to the rich faster than new investment opportunities arise, then the rich people will have more money to bid against each other for assets like stocks. It's easier than ever to trade stocks and there's more and more information about it, meaning more and more people are investing in businesses. The US trade deficit means there's more foreign capital inflow, which is propping up asset values as well, not just stocks but real estate too.

I suspect QE might play some role in stock market prices too, the Fed's been printing an awful lot of money (although a lot of it's been used to shore up bank balance sheets rather than being used to buy stocks). Also, interest rates have been low for a long time. Meaning money that used to buy bonds is buying stocks instead, which pushes up the price of stocks. And now that the Fed's thinking about raising rates, there may be something of a rush to get out of bonds before it happens.