Prof. Robert Shiller of Yale University invented the Schiller P/E to measure the market’s valuation. The Schiller P/E is a more reasonable market valuation indicator than the P/E ratio because it eliminates fluctuation of the ratio caused by the variation of profit margins during business cycles. This is similar to market valuation based on the ratio of total market cap over GDP, where the variation of profit margins does not play a role either.
GuruFocus calculates the Shiller P/E ratio of individual stocks and different sectors. Here you can see the Sector Shiller PE, it shows you which sectors are the cheapest. Here you can see Shiller P/E of individual stocks.
Everyone who is still in the stock market is extremely happy. And why not? The market is at an all time high, profits are up, unemployment is down and Trump mania is sweeping through the manufacturing sector: Making America Great Again.
Do I regret getting out of the market in 2009? Do I regret losing potential money by not being in the market? No. For the same reason that I do not gamble: the house always wins. Even if the game is not rigged by central banks.