Fewer Americans hit the malls the last week before Christmas even as retailers poured on the discounts, Bloomberg reported. U.S. store visits plummeted 21 percent and retail sales dropped 3.1 percent in the week through Dec. 22, signaling a lackluster finish for stores' most important selling season, Chicago-based researcher ShopperTrak said. Falling store traffic in recent weeks and uneven demand, especially for apparel, spurred chains to risk earnings by piling on the discounts to generate sales. Retailers including Neiman Marcus Group LLC were offering as much as 75 percent off, and some, including Macy's Inc. and Kohl's Corp., were keeping stores open around the clock starting Dec. 20. At the same time, Americans are increasingly shopping online.