Walmart on Tuesday reported a lower-than-expected quarterly profit. The company posted a sharp drop in online sales growth during the critical holiday period, which sent its shares tumbling more than nine percent. Even as comparable sales in the U.S. market rose for the 14th consecutive quarter, Walmart’s online sales grew 23 percent in the holiday quarter. The category grew 29 percent in the same period a year ago, and 50 percent sequentially from the third quarter.