I'm basically in the Shiller camp. Corporate profits have been unusually high for the last few years, as weak firms went out of business and firms shed their workforce. The S&P 500's price-to-earnings ratio is in the high end of its historical range. It's still within its historical range, to be sure, but after a punishing recession, and with further storm clouds on the horizon, that seems to me to point to a least some level of overvaluation. That doesn't necessarily mean it will fall. Rather, it means that it is more likely to deliver lower returns in the future.