Using a unique data set of transaction-level retail food sales, I find that food prices are negatively related to supermarket chainsâ€™ shares of total U.S. food sales. The negative relationship suggests that supermarket chains enjoy economies of scale or benefit from an improved post-merger bargaining position. In contrast, the regressions also show an increase in price after a merger, which is independent from changes in observable control variables. Subsequent fractional logit analysis suggests mergers are associated with decreases in the frequency and depth of price-promotions. These latter effects suggest supermarkets enjoy greater unilateral pricing power post-merger, perhaps due to improved brand identity.