"Tobin's q"

Stocks, too, seem pricey. Over the past 130 years, U.S. stocks on average have traded at about 17 times mean earnings for the previous 10 years—a measure known as the "Shiller Price/Earnings Ratio" after Yale economics professor Robert Shiller, who tracks the data. Today the market is about 22 times those earnings, a level associated with frothy markets such as 1929, the mid-1960s, and most of the period from 1995 to 2008.

Another measure, "Tobin's q," also suggests stocks might be in dangerous territory. Tobin's q, named for the late Nobel economics laureate James Tobin, measures stock valuations against the cost of replacing companies' assets. Right now the reading is 0.92, about 50% above the long-term historical average. Stock returns from these levels have usually been subpar.

It's Time to Time the Market
by Brett Arends
http://online.wsj.com/article/SB10000872396390443624204578060550181314438.html