WASHINGTON (AP) — The U.S. economy slowed more sharply in the final three months of the year than initial estimates, reflecting weaker business stockpiling and a bigger trade deficit. The Commerce Department said Friday that the economy as measured by the gross domestic product grew at an annual rate of 2.2 percent in the October-December quarter, weaker than the 2.6 percent first estimated last month. Consumer spending, which accounts for 70 percent of economic activity, was a bright spot in the fourth quarter. Naroff and other economists believe the key to the economy shifting into a higher gear will be further improvements in the labor market, when stronger job gains leading to rising wage gains. News last week that Wal-Mart, the nation's largest private employer, would also increase its minimum pay could be a sign that a tighter labor market are finally leading to increased wages, some analysts believe. Federal Reserve Chair Janet Yellen, testifying to Congress this week, listed stronger wage growth as one of the elements the central bank is looking for before deciding to start raising interest rates.