Will The S&P Cyclically Adjusted P/E Ratio Overshoot To The Downside? (Robert Shiller, Chart)

Shiller Cyclically Adjusted P/E Ratio (interactive chart below)
Dr. Robert Shiller, Yale economics professor and co-founder of the Case-Shiller Home Price Index, was interviewed by Aaron Task and Henry Blodget on Daily Ticker on 9/27/2011. He is still "worried" that stock valuations could overshoot to the downside. I embedded the video after the jump.

What do you think? When looking at Shiller's CAPE (cyclically-adjusted P/E ratio), is it time for the stock market to trade under its long-term average P/E multiple and overshoot like it did in the 1920s, 1930s and 1980s? Or will it happen in another decade? Shiller has data available to the public online going back to 1881. You can chart out the S&P 500, dividend, earnings, consumer price index, long-term interest rate and more in excel format. Below is an interactive chart of the cyclically-adjusted P/E ratio going back to 1881 in log scale. For more on this topic, see Shiller's recent interview on Fox Business and read John Hussman's recent note on the possibility of secular undervaluation (and where the market could trade).

Source: http://finance.yahoo.com/blogs/daily-ticker/robert-shiller-stock-prices-still-high-historic-standards-124130870.html

Source: http://www.econ.yale.edu/~shiller/data.htm