Antitrust authorities are interested to know whether airline companies use their market power to charge higher fares in the U.S. A dataset called airlinefares2000.xls is provided with this problem set and consists of average fares and other characteristics of the most popular U.S. origin-destination pairs (e.g. Boston-Chicago) for the year 2000: lfare is log of the average fare on the given route (log of dollars), dist is distance of the route (in thousand miles), passen is number of average passengers per day (in thousands), concen, that is concentration is the market share of the biggest airline carrier on the given route measured in terms of passengers carried (range is 0.1 to 1). Regress lfare on dist, passen and concen, and provide the heteroskedasticity-robust standard errors.