Effects of antitrust prosecution on retail fuel prices

In February 2015, Spain’s Competition Authority imposed € 32.4 million in fines on five of the country’s largest oil operators as sanctions for price collusion. This paper examines the effect of that antitrust action on retail fuel prices. Our analysis uses a novel data set with detailed information on more than 8000 gas stations throughout Spain. Prices were collected every day from 18 August 2014 to 15 June 2015 (almost 2 million price observations). First we estimate a reduced-form fuel price equation that accounts for wholesale costs and brand affiliation. Then we use a model of gas stations and time fixed effects while adopting a difference-in-differences approach to assessing the fines’ effect on retail fuel prices. Our results indicate that, after publication of the fine, sanctioned firms raise prices slightly, and the additional revenues far exceeded the amount of the fine. We also find substantial heterogeneity, depending on the size of the fine, in the magnitude of this price response. Hence the fine’s burden might well have been borne mainly by consumers, whose welfare was thereby reduced. Our study should be of interest to antitrust authorities as we show that sanctions may not be effective enough in deter price fixing practices, especially when sanctions are weak and the profits from colluding are sufficiently high.