US private companies added workers at a brisk clip in December, pointing to underlying strength in the economy despite signs that growth slowed sharply in the fourth quarter. Other data on Wednesday showed the U.S. trade deficit narrowed in November likely as efforts by businesses to reduce an inventory overhang pushed imports of goods to their lowest level in nearly five years, outpacing a drop in exports. Payrolls processor ADP said private-sector employment rose by 257,000 last month, the largest gain since December 2014, after increasing by 211,000 in November. However, the ADP ...