Industrial production rose 0.6 percent in December as unusually cold weather helped energy utilities offset a small drop in manufacturing.
The mixed picture from Friday's report by the Federal Reserve shows that economic recovery remains uncertain, as consumers and businesses did not spend enough to spur the production of more factory goods.
It was the sixth straight monthly gain and was in line with economists' expectations.
Electric and gas utilities increased production by 5.9 percent and mines by 0.2 percent. Manufacturers produced 0.1 percent less than in November.
Construction and consumer durable goods posted losses of 2.0 percent and 0.9 percent, respectively, while paper products output fell 0.9 percent.
Still, industrial production for the fourth quarter as a whole increased at an annual rate of 7.0 percent, reflecting the economy's swing toward growth.
The economy grew at an annual 2.2 percent in the third quarter, and was expected to continue growing through the end of 2009.
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