I'm still a believer because, take a look at the large scope of history, the '80s and the '90s were the greatest bull market the world has ever known and we ended in a bubble. Stocks were overvalued then. One thing we know about stock prices is reversion to the mean, and it's usually with a vengeance, which means if you overshoot on the topside you're gonna subsequently overshoot on the bottom side. And that's what happened in the first decade of this millenium, we went from extremely overvalued to March of 2009 we were extremely undervalued.
I still think we're undervalued. My historical studies say this is really a time to pick up stocks.
~Jeremy Siegel, professor of finance, Wharton School, CNBC "Street Signs", October 19th, 2010