What is Cyclically Adjusted Price-to-earnings Ratio?

Legal Definition
The cyclically adjusted price-to-earnings ratio, commonly known as CAPE, Shiller P/E, or P/E 10 ratio, is a valuation measure usually applied to the US S&P 500 equity market. It is defined as price divided by the average of ten years of earnings (moving average), adjusted for inflation. As such, it is principally used to assess likely future returns from equities over timescales of 10 to 20 years, with higher than average CAPE values implying lower than average long-term annual average returns. It is not intended as an indicator of impending market crashes, although high CAPE values have been associated with such events.
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