With investors returning from last-minute summer vacations, the coming week could be a telling one as August's thin markets end and more earnest stock market trading resumes.

Last week, on light trading volume, the

Dow Jones Industrial Average

finished the week down 2.4% at 8663, the

S&P 500

fell 2.6% to 916, and the

Nasdaq

lost 4.7% to 1315.

"August was a stabilizing month," said Joel Naroff, an economist at Naroff Economic Advisors. "In September, the tone will be set early."

But there's something of a cloud hanging over the coming month. According to the

Stock Traders Almanac

, over the past 51 years the Dow and the S&P have, on average, ended September slightly lower. The same is true for the Nasdaq over the last three decades.

"I can't see the stock market picking up momentum, particularly after the holiday, and people will start to begin to clear out their portfolios," said John Silvia, chief economist at Wachovia Securities. Silvia added that he's expecting companies to come out with more downward revisions of their future earnings projections.

Big Numbers

Economic data that should help determine the market's direction include the August

employment numbers, due out Friday. The number is always key. In recent months, the economy has been growing, but so far not enough to create new jobs. That's led some observers to raise the possibility of an economic recovery without strong job growth, which could put consumer spending at risk.

The expectation is that 30,000 new nonfarm jobs were added to payrolls in August and that unemployment held steady at 5.9%.

"This modest type of employment scenario tells consumers that there aren't a lot of new jobs being created out there and there's only moderate economic growth," Silvia said.

The Institute for Supply Management's

manufacturing index will shed some light Tuesday on how the factory sector is performing. Analysts expect the ISM survey to come in at 51, up from 50.5 a month ago, but forecasts could be revised upward after the

durable goods orders and

Chicago purchasing managers' index both came in better than expected last week. A reading of 50 or above means the manufacturing sector is expanding.

"We think it could be 53," said Stephen Stanley, senior market economist for Greenwich Capital Markets. "After the Chicago numbers, we raised our forecast 2 points."

Silvia isn't as optimistic. "I think it will show that manufacturing is sluggish," he said. "

Manufacturers don't see strong futures sales, and they need to keep inventories under control."

Chip Talk

Construction spending for July, which comes out Wednesday, is expected to decline. Despite strong residential construction, commercial construction is seen as a laggard that has yet to see real growth. July construction spending is expected to dip 0.5%. It decreased 2.2% in June.

According to consensus estimates, experts believe August

vehicle sales will fall, but they could still be a bright spot next week. Analysts are looking for auto sales to come in at 6.2 million, with truck sales totaling 7.9 million.

For the most part, quarterly earnings have been reported, but a small group of companies remain, including

Campbell Soup

(CPB) - Get Report

. But the big update will come from chip giant

Intel

(INTC) - Get Report

, which is hosting a midquarter review Thursday.