Brown Bag Seminar Industrial Economics

This paper examines the “right” geographic definition of relevant markets by analysing how excise tax pass-through varies with local competition in the retail gasoline market of Athens, Greece. Using a natural experiment from three unanticipated and exogenous fuel tax hikes in 2010 and detailed station-level price data, we show that average pass-through is almost complete and invariant to the number of nearby competitors across various geographic definitions. This contrasts with theoretical predictions and prior island-based evidence, suggesting that the entire metropolitan area functions as a single market. Our findings challenge standard isodistance or isochrone-based market delineations used in academic research and competition policy.