How Could the Market Possibly be Overvalued After the Great Recession?

This would, on the face of it, seem to be an unusual question to ask after the Global Financial Crisis. How could the stock market possibly be overvalued? In the video above, Prof. Robert Shiller thinks that, based on longer historical analysis of P/E ratios, the market is overvalued. Prof. Siegel, on the other hand, thinks not. There are other players in the debate: David Bianco of Bank America Merrill Lynch (Shiller's data is questionable) and David Arnott of Research Affiliates (he likes Prof. Shiller's approach to earnings analysis). You can read the entire debate in the Wall Street Journal (here).