Supermarket giant Kroger ( KR ) said Thursday that an ongoing slump in grocery prices was largely responsible for its surprise drop in same-store sales, and the company said the market environment it's in now could persist through the first half of this year. Kroger said it expected conditions in the first half of this year to be "similar" to the back half of last year. At that time, lower food prices were a big topic of discussion during earnings calls in the grocery industry. The company added that its results in the second half of 2017 "are expected to show improvement as the company cycles the previous year." However, management also said it expected the market to become "more competitive." Wal-Mart ( WMT ), which draws much of its sales from groceries, began a price-cutting crusade last year. Target ( TGT ), which also sells groceries, said last month that it would lower prices and that retailers were navigating a "seismic shift" in their industry.