The economy expanded in the third quarter at the fastest rate in almost two years as Americans stepped up spending on services such as health care and companies invested more in software.

Gross domestic product climbed at a revised 4.1 percent annualized rate, the strongest since the final three months of 2011 and up from a previous estimate of 3.6 percent, Commerce Department data showed Friday in Washington. The gain exceeded the most optimistic projection in a Bloomberg survey.

Inventories accounted for a third of the increase in GDP in the third quarter, showing companies were confident about the prospects for demand. Stronger retail sales in October and November underscore the Federal Reserve's view that the world's largest economy is improving.

"You have equity markets supporting household net worth, rising home values and also payroll gains and falling unemployment, so we do really look for consumption to start picking up," said Robert Rosener, associate economist at Credit Agricole CIB in New York, whose forecast for growth of 3.8 percent was the highest in the Bloomberg survey. "This is a very good sign for momentum going into the fourth quarter."

The median forecast of 72 economists surveyed by Bloomberg projected a 3.6 percent gain in GDP, the value of all goods and services produced in the U.S. Forecasts ranged from 3.3 percent to 3.8 percent.

Stocks rose after the figures, with the Standard & Poor's 500 Index advancing 0.6 percent to 1,820.78 at 11:46 a.m. in New York.

Consumer purchases, which account for almost 70 percent of the economy, increased 2 percent, more than the previously reported 1.4 percent, the revised data showed.

Spending on services contributed 0.32 percentage point to third-quarter growth, up from a previously reported 0.02 percentage point. In addition to the pickup in outlays for health care, Americans spent more on recreational services.

Outlays for non-durable goods climbed at a 2.9 percent rate in the third quarter, led by more spending on gasoline.

Inventories increased at a $115.7 billion annualized pace in the third quarter, the most in three years, after a previously reported $116.5 billion annualized rate. In the second quarter, they rose at a $56.6 billion pace.

Stockpiles added 1.67 percentage points to GDP last quarter, little changed from the 1.68 percentage-point contribution in the previous reading.

While economists grew more optimistic about demand in the fourth quarter, GDP will nonetheless be restrained as the pace of inventory growth cools.

JPMorgan Chase & Co. economists project the economy will grow 2 percent from October through December, up from the 1.5 percent rate they had penciled in prior to the Commerce Department's Dec. 12 retail sales report. Barclays Plc has raised its fourth-quarter tracking estimate to 2.3 percent from 2 percent before the retail figures.

Domestic final sales, which exclude inventories, increased 2.5 percent in the third quarter compared with a previously reported 1.9 percent increase.

Corporate spending on equipment rose 0.2 percent, compared with a previous reading of no change. Business investment in intellectual property was revised up to a 5.8 percent increase from 1.7 percent, reflecting more spending on software.

Further investment will depend on how much confidence companies have that the economy will accelerate.

Honeywell International Inc., whose products range from cockpit controls to thermostats, expects capital expenditures in the range of $1.2 billion or more in 2014, up about 30 percent from this year.

"We're very disciplined in terms of cap-ex," Chief Financial Officer David Anderson said on the company's 2014 guidance call on Dec. 17, referring to capital expenditures. "We really have to see the whites of the eyes of the economic return characteristics to really commit."

Economic indicators "are pointing to just a continued resilience, not exuberance, but resilience and expansion in the U.S. economy," Anderson added.

Friday's report also included corporate profits. Before-tax earnings rose at a 1.9 percent rate after climbing at a 3.3 percent pace in the prior period. They increased 5.7 percent from the same time last year.

Residential real estate is underpinning the economy, as rising prices boost household wealth and growing demand helps the industry overcome rising mortgage rates.

Home construction increased at a 10.3 percent annualized rate in the third quarter. While slower than the 13 percent pace previously reported, the figure primarily reflected revisions to brokers' commissions and other ownership transfer costs, Friday's report showed.

Data from the Commerce Department this week showed that housing starts jumped 22.7 percent to a 1.09 million annualized rate, the most since February 2008, while permits for future projects also held near a five-year high, indicating that the pickup will be sustained into next year.

Other signs show that fiscal drag, which weighed on growth during 2013, will start to ease. U.S. lawmakers this week passed the first bipartisan federal budget produced by a divided Congress in 27 years, easing $63 billion in automatic spending cuts and averting another government shutdown.

Government outlays increased 0.4 percent in the third quarter, led by a 1.7 percent gain in state and local spending that was the same as the previous reading. Federal spending decreased 1.5 percent.

Tighter fiscal policy has made stimulating the U.S. economy even more of an uphill battle for the Fed. The central bank this week announced it would scale back its bond-purchase program by $10 billion, to $75 billion a month, after seeing an improved outlook for the labor market.

"This has been done in the face of a very tight, unusually tight fiscal policy for a recovery period," Chairman Ben Bernanke said Dec. 18 during a press conference at the conclusion of a meeting of the Federal Open Market Committee.

With assistance from Chris Middleton in Washington.