Watching and waiting for the first signs of economic recovery is becoming a Wall Street obsession. Investors who correctly predict a rebound could make a fortune. Those who move too late or too early could lose out.

One way to peer into the future is economic data. New reports on May 13, for example, showed a 1% drop in March business inventories and a 0.4% fall in retail sales in April. The disappointing data, which ran counter to the "green shoots" of recovery evident in other recent reports, helped send major stock indexes solidly lower on May 13.

But another way is to look at the stock market itself, watching industries and sectors that are good leading economic indicators. BusinessWeek asked investment pros which parts of the market will serve as reliable economic weather vanes. This question is complicated by worries about false starts, as well as the suspicion by many that a recession this serious will not end in the same way as previous, more typical downturns.

1. Energy and Basic Materials

"Commodity stocks should be the first ones to rally," says Bruce Bittles, chief investment strategist at R.W. Baird. A reviving economy needs more raw materials and energy.

Some of these stocks already have rallied. The Standard & Poor's energy sector as a whole is down 7% in 2009, but a recent rally has put the oil and gas drilling industry up 19% for the year. Materials stocks are up 16.5% in the past week.

But commodities markets are not infallible. Oil prices hit a record peak last year just a few months before the world economy slipped into recession. Gary Wolfer, chief economist at Univest Wealth Management (UVSP), calls the commodities and energy rebound a "false start." In areas like natural gas, for example, Wolfer attributes the bounce-back not to the economic recovery but to "production finally being brought in line with demand."

2. Transportation Stocks

Whenever the economy heats up, the nation's shippers will get busy. Shipping volumes plunged in late 2008 when the economy ground to a halt. According to Longbow Research, a survey of truckers released May 11 offered some hope. In March, 64% of truckers surveyed had a negative outlook for demand, and by April that had subsided to 39%.

But full-blown optimism might not be warranted, according to Longbow analyst Lee Klaskow.