NEW YORK—American consumers can expect bigger grocery bills in 2012, even as commodity prices are forecast to fall. (snip) In a recent report, the U.S. Department of Agriculture said grocery-store prices will likely rise 3% to 4% in 2012, on par with this year, even though ingredient costs may fall. The biggest increases would likely be in the first half of next year, but prices would most likely ease later in 2012, said USDA economist Richard Volpe.