 When NPR asked listeners this summer where inflation stings the most, grocery prices was one of their top concerns. Sure, those prices have inched up only about 1% in the last year or so, but food economist David Ortega of Michigan State University notes that's on top of a nearly 6% increase the previous year and a jump of almost 12% the year before that. What consumers are reacting and feeling is the cumulative effect of inflation. Another factor is that unlike other prices,