Don’t worry too much about supply and demand at the supermarket.

Two Federal Reserve economists have found grocery stores don’t tend to jack up or slash their prices in response to big shifts in customer traffic caused by winter storms, hurricanes, picket lines and major natural disasters.

“Our key finding is that large swings in demand appear to have, at best, a modest effect on the level of prices, consistent with a flat short- to medium-term supply curve in the retail industry. This finding holds even in the case of our most persistent shocks for which stores adjusted the price of most items multiple times (or at least a couple of times in the case of regular prices),” wrote Etienne Gagnon and David Lopez-Salido, both economists at the Fed in Washington, in a recent working paper.