Updated

The U.S. economy grew at a 3.6 percent annual rate from July through September, the fastest since early 2012. But nearly half the growth came from a buildup in business stockpiles, a trend that could reverse in the current quarter and hold back growth.

The Commerce Department's second estimate of third-quarter growth was much higher than the initial 2.8 percent rate reported last month. And it was well above the 2.5 percent growth rate for the April-June quarter.

But almost the entire third-quarter revision came from a big jump in stockpiles. Consumer spending, the lifeblood of the economy, was the weakest in nearly four years.

When excluding inventories, the economy grew at a 1.9 percent rate in the third quarter, down from 2.1 percent in the spring.