What is the “right” geographic market definition?
通过分析大城市零售汽油市场中消费税转嫁如何随本地竞争变化，发现整个都市区是一个单一市场，挑战了传统基于距离或时间的市场划分方法。
This paper examines the “right” geographic definition of relevant markets by analyzing how excise tax pass-through varies with local competition in the retail gasoline market of a large metropolitan city. Using a natural experiment from three unanticipated and exogenous fuel tax hikes and detailed station-level price data, we show that average pass-through is 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.