It is from memory, the 27 number is from memory from around August 87, when I decided to get out, mostly because I became very busy with other business, and that number seemed a little high 30 years treasuries still in the stratosphere of 8% to 9% (and going back up). Not so much good timing, more luck I would guess.
Quoting a range of PE from 10 to 20 with 15 as neutral, 10 as bullish and 20 as bearish would keep you in bear market for much longer than necessary and out of bull markets. Since the beginning of the 90' the SPX pe was never under 15, so you would be out of the greatest bull. From 1966 to 1982, the last secular bear market, we rarely saw that pe going into "danger territory" above 20, yet 16 years of prices going essentially downhill with few cyclical bull markets in between.
PE are particularly useless unless compared with competing investments, risk free treasuries. People that put these charts should "normalize these with the then prevailing long term interest rates and they will see much clearer calls.
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