After the sharp run-up in stock prices during the bull market of the late 1990s and their subsequent collapse in 2001–2002, the prices of equities as measured by the S&P 500 are once again uncommonly high relative to companies' current and prospective earnings, causing some to question whether they are too high relative to the underlying value of the companies they represent.

This paper compares the recent performance of the equities constituting the S&P 500 with their performance since the 1940s and then extends the familiar Gordon model of equity pricing to examine the contributions of the factors that are likely to influence stock prices in the future. The authors conclude that current valuations do not necessarily indicate a bubble: Rapidly growing earnings and high returns on capital, consistent with a return to full employment, could justify prevailing prices.