The U.S. economy stayed afloat in the third quarter despite global turmoil, but it's struggling to break out of the slow-growth pace that has plagued the economic expansion.

The economy grew at a modest 1.5% seasonally adjusted annual rate from July through September, the Commerce Department said Thursday. That marked a deceleration from the second quarter, when U.S. gross domestic product—the broadest measure of economic output—expanded at a 3.9% pace.