The Shiller cyclically adjusted (for inflation) price-to-earnings ratio—referred to as the CAPE 10 because it averages the last 10 years’ earnings and adjusts them for inflation—is a metric used by many to determine whether the market is undervalued, fairly valued or overvalued. Employing a 10-year average for earnings, instead of the most current 12-month earnings, was first suggested by legendary value investors Benjamin Graham and David Dodd.
In their classic 1934 book “Security Analysis,” Graham and Dodd noted that traditionally reported price-to-earnings ratios can vary considerably because earnings are strongly influenced by the business cycle. To control for the cyclical effects, Graham and Dodd recommended dividing price by a multiyear average of earnings and suggested periods of five, seven or 10 years.
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