For a more precise view of how today's P/E10 relates to the past, our chart includes horizontal bands to divide the monthly valuations into quintiles — five groups, each with 20% of the total. Ratios in the top 20% suggest a highly overvalued market, the bottom 20% a highly undervalued market. What can we learn from this analysis? Over the past several months, the decline from the all-time P/E10 high has dramatically accelerated toward value territory, with the ratio dropping from the 1st to the upper 4th quintile.
A more cautionary observation is that every time the P/E10 has fallen from the first to the forth quintile, it has ultimately declined to the fifth quintile and bottomed in single digits. Based on the latest 10-year earnings average, to reach a P/E10 in the high single digits would require an S&P 500 price decline below 600. Of course, a happier alternative would be for corporate earnings to make a strong and prolonged surge. When might we see the P/E10 bottom? These secular declines have ranged in length from over 19 years to as few as three. The current decline is now in its ninth year.
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