THE STOCK market’s stunning gains in the last year make it easy to assume these must be the best of times for the U.S. economy. But government GDP figures tell quite a different tale.

It’s a good lesson in economics. Wall Street’s surge is being fueled by stronger-than-expected corporate profits, which assess how business is going here and abroad. Gross domestic product, in turn, only tracks U.S economic activity and does so by a different yardstick.