Gross domestic product — or the output of goods and services in the U.S. — increased at an annual rate of 2.7% in the third quarter, according to the second estimate from the Commerce Department.

That is not the final estimate, but it's already above the initial 2% estimate for the period and early estimates that growth would top out at the 1.9% level for the third quarter.

It's also much improved from the second quarter when the economy grew at a slower 1.3% rate.

The Bureau of Economic Analysis at the Department of Labor noted the growth resulted from personal consumption, inventory investment, federal government spending and residential-fixed investments.

Despite the number showing growth, Econoday analysts worry the increase is largely due to higher estimates for inventory nonresidential structures and exports.

"Notable downward revisions were seen in consumer spending and business equipment," Econoday said. "Estimates for residential investment and government purchases were little revised."

The research firm added, "Overall, the headline GDP number looks good but the detail raises questions about the sustainability of the recovery."