hi sg
I have to say that I think use of "reversion to the mean" as a stock investment indicator is pure horse puckey.... Observed "reversion to the mean" may not happen for many years and that "reversion" could happen at a time when the mean is even higher than it is today.
If you need any consolation that you are not alone in the view that mean reversion might not be a certainty useful to investors, there is always SSRN:
http://papers.ssrn.com/sol3/papers.cfm?abstract_id=683182
You have to read the paper to determine if you agree with their approach but here are a couple quotes to spark interest:
"Perhaps most interesting, however, is that the nonstationarity of the E/P ratio suggests that this valuation measure can remain below its mean for an extended period of time, and that its reciprocal, the market P/E, can stay above trend for extended periods - and possibly forever, at least theoretically. The P/E ratio's shift from a stationary to a nonstationary series ca. 1960 implies that it no longer has a mean to which it must revert."
...
"It is clear from examining the graph that the general negative relation between starting P/E ratios and 10-year real returns abruptly truncates at P/E ratios greater than 21. Ten-year returns starting from very high P/E ratios have never been severely negative. Although the overall trend of the P/E and stock return relation is negative, the lowest 10-year real returns are earned starting from market P/E ratios between 12 and 20. Significant declines in the value of U.S. equities starting from high levels of the market P/E ratio are rare."
hix9
I have to say that I think use of "reversion to the mean" as a stock investment indicator is pure horse puckey.... Observed "reversion to the mean" may not happen for many years and that "reversion" could happen at a time when the mean is even higher than it is today.
If you need any consolation that you are not alone in the view that mean reversion might not be a certainty useful to investors, there is always SSRN:
http://papers.ssrn.com/sol3/papers.cfm?abstract_id=683182
You have to read the paper to determine if you agree with their approach but here are a couple quotes to spark interest:
"Perhaps most interesting, however, is that the nonstationarity of the E/P ratio suggests that this valuation measure can remain below its mean for an extended period of time, and that its reciprocal, the market P/E, can stay above trend for extended periods - and possibly forever, at least theoretically. The P/E ratio's shift from a stationary to a nonstationary series ca. 1960 implies that it no longer has a mean to which it must revert."
...
"It is clear from examining the graph that the general negative relation between starting P/E ratios and 10-year real returns abruptly truncates at P/E ratios greater than 21. Ten-year returns starting from very high P/E ratios have never been severely negative. Although the overall trend of the P/E and stock return relation is negative, the lowest 10-year real returns are earned starting from market P/E ratios between 12 and 20. Significant declines in the value of U.S. equities starting from high levels of the market P/E ratio are rare."
hix9