Here’s an interesting post on the P/E ratio method of valuing the market over the past 100 years. Using the Schiller method, the S&P is trading at an 11.85 P/E. That’s well below the long term average 16, so the markets are oversold, but still above the level were markets bottomed in major downturns in the past.
So, if you have a long-term perspective, you could buy and have a reasonable expectation of coming out ahead in the long run. But there could still be some decent downside in the meantime.
Another post from the same site shows that, on an inflation-adjusted basis, the DOW is the same today as it was in 1966. Flat for 43 years. “Stocks for the long run, indeed.”