LONDON - Unilever PLC, the world's second-largest consumer-goods maker, reported fourth-quarter revenue growth that missed estimates and said it expects difficult economic conditions and elevated commodity costs to persist this year.

So-called underlying sales, which exclude acquisitions and currency fluctuations, rose 6.6 percent in the three months through December, the London- and Rotterdam-based company said in a statement on Thursday. The average estimate of 28 analysts compiled by Unilever was 6.8 percent. The quantity of goods sold gained 0.1 percent, while prices increased 6.5 percent.

"We cannot recollect a more challenging year as 2011," Chief Financial Officer Jean-Marc Huet said on Thursday. "The global economy is still in poor shape, and we expect it to continue."