A year that started in gloom and doom could end in cheers for U.S. corporate profits and leave the stock market positioned for a strong start to 2010.

Analysts have been forecasting a big jump in fourth-quarter earnings compared to a year earlier when the entire Standard & Poor's 500 index ended in a per-share loss.

Expectations for the fourth quarter have jumped even further as four out of five companies have exceeded forecast results in the third quarter.

S&P companies now are expected to show a gain of 205 percent from a year ago, compared with early October estimates for a gain of 193 percent, according to John Butters, director U.S. earnings at Thomson Reuters.

The S&P as a group is expected to earn $17.10 a share in the fourth quarter, compared with an estimate of $16.52 at the start of the month, he said.

While some companies may be experiencing a rebound, the biggest element in the spectacular increase is last year's abysmal performance when the economy was in the depths of the recession, analysts said.

More upward revisions could be ahead, they said.

Assuming that our economic forecast for continued recovery proves valid, there seems to be room for these future expectations to move higher, analysts at PNC Financial Services Group in Philadelphia said in a note.

The earnings outlook continues to be supportive of stocks.

A stronger economy signals a stronger corporate America. The S&P index is up 57 percent since its lows in early March, with the market responding favorably to both upbeat earnings news and economic data.

The economy grew faster than expected in the third quarter, expanding at a 3.5 percent annual rate, gross domestic product data showed on Thursday. The report suggested the economy is emerging from its recession.

The fourth quarter is expected to mark the first quarter that S&P 500 company earnings grew year-over-year since the second quarter of 2007.

So far in the third quarter, some 81 percent of S&P companies have beaten earnings expectations, well ahead of the 61 percent in a typical quarter, and a new record, Butters said.

Earnings in the first and second quarters handily beat expectations, and so far in the third quarter, estimates have improved quickly since October 1.

Third-quarter earnings are now seen declining 17.9 percent compared with October 1 expectations for a 24.7 percent decline.

I'm watching the (fourth-quarter) estimates continue to rise at a fairly rapid rate. At some point, the number of positive surprises will start to slow, said Fred Dickson, market strategist at D.A. Davidson & Co. in Lake Oswego, Oregon.

That companies have been low-balling their own expectations has allowed profits to beat analysts' estimates, strategists said.

Clearly the economy is starting to improve, and these companies by and large have been setting a very low bar, and have been talking the numbers down so that they don't disappoint, said Stephen Massocca, managing director of Wedbush Morgan in San Francisco. Now it's becoming clear that's what they've done, so the estimates are coming up to a more normalized (level).

Critics of the upbeat earnings view argue that profit beats have come from drastic corporate cost-cutting and not from sales growth.

I don't expect to see universal revenue growth in the fourth quarter, and so I think it'll still be a market where companies talk about cost cutting and the market talks about companies beating (estimates), said Subodh Kumar, chief investment strategist at Subodh Kumar & Associates in Toronto.

A number of high-profile companies, including General Electric (GE.N: Quote, Profile, Research, Stock Buzz), have suggested growth may be slower than expected in coming quarters.

Also, there are concerns that government stimulus efforts are largely responsible for a temporary bump in demand.

A turnaround in revenue is projected for the fourth quarter. S&P 500 revenue is estimated to decline 9.9 percent for the third quarter but rise 6 percent in the fourth quarter, according to Butters.

I'm under the belief the sharper the fall, the higher the bounce. I think people are going to be surprised at the strength of the recovery, said Mark Travis, president and chief executive of Intrepid Capital Funds in Jacksonville Beach, Florida.

(Editing by Kenneth Barry)