John Hussman says about this chart:

Based on our standard methodology (see The Likely Range of Market Returns in the Coming Decade for the basic approach) we estimate that the S&P 500 is priced to achieve a 10-year total return of just 5.05% annually. Using our forward operating earnings methodology (see Valuing the S&P 500 Using Forward Operating Earnings), the projected 10-year total return is just 4.69% annually. With the S&P 500 dividend yield at 1.96%, the 10-year projection from dividend-based models is even lower, at about 2.30% annually (though prospects are good that faster growth of index-level dividends will bring that estimate closer to earnings-based projections, see No Margin of Safety, No Room for Error).

Overall, the projected returns for the S&P 500 are now lower than at any time in U.S. history prior to the bubble period since the late-1990’s (which has resulted in predictably dismal returns for investors). At present, investors rely on a continuation of this bubble to achieve further returns. With respect to the bubble period, the current projected returns match those we observed at the April 2010 high, and are at about the same level as we observed before prices collapsed in 2008. Valuations were even more extreme, of course, at the bubble peak of 2000, which was predictably followed by a decade of zero returns.

Keep in mind that near-term returns much higher than 5% annually would essentially be shifted from future years, meaning that higher returns today simply imply even lower long-term return prospects tomorrow. For very long-term investors, say 15 years or more, such variations hardly matter. By our estimates, investors are looking at prospective 15-year total returns in the range 5.8-6.5% annually, with enormous volatility in the interim, no matter how you cut it.