Morningstar.com Market Valuation Graph

Want to know if the U.S. stock market is too high or too low? Here is a free chart you can follow.

With more than a decade of published track record, the Market Valuation Graph at Morningstar.com gives Morningstar's current calculations of  net present value of the stock market -- what their analysts calculate the market is worth today based of expected dividends and growth over the next several years.

Here is the link.  I prefer using the "max" time period setting.
http://www.morningstar.com/market-valuation/market-fair-value-graph.aspx

There are probably worse investment strategies than to respond every couple of years to extremes in the net present value calculations that Morningstar compiles and presents here for a vast universe of stocks and then averages together.  Put another way, be careful if you think the stock market is valued far away from the Morningstar estimates -- their track record has been amazingly good.

The strategy to using this measure is simple: 

Buy more stocks when Morningstar calculates that the market in undervalued by, say, 10% or more.
Sell some stocks when Morningstar views the market as overvalued by, say, 8% or more.

Then be patient.  It is difficult or impossible to predict exactly when the market will turn course, but this graph shows that year-to-year pricing of the stock market tends to revert toward the neutral "fair market value".