Unlike other popular valuation metrics, which measure the level of the S&P 500 against expected earnings, sales, cash flow or some other metric, the CAPE ratio takes the level of the S&P 500 and divides it by the average inflation-adjusted earnings of its constituent companies over the past decade.The CAPE ratio, a popular valuation metric devised by Yale economist Robert Shiller, has been pressing higher since the bull run began. It stood just shy of 38 as of late August, a level it hasn’t visited since la ...