Consumer prices in the U.S. are barely rising, a boon to shoppers for everything from computers to clothing and a big reason that the Federal Reserve is willing to keep interest rates exceptionally low a while longer. Because of a spurt in energy prices, the consumer-price index rose 0.2% in January and has climbed 2.6% over the past 12 months, the Labor Department said Friday. But stripping out volatile food and energy prices, as policy makers do to gauge underlying trends, consumer prices actually fell by 0.1% in January, the first time that has happened since 1982. That so-called core-inflation measure was up a meager 1.6% in the past 12 months.