suffers from being at the end of the supply lines.  The refining surplus area is the USGC.  There are a bunch of pipelines up into the midwest but by the time you get to MI there are damn few players and not that many ways to resupply the market.

Makes for an easy place to just choose not to compete very hard or not at all.  No trader is going to spend much time figuring out ways to arbitrage gas into Michigan to capture the extra profit.

Same situation on the west coast.  Few players, remote to re-supply markets, special specs reducing fungibility of the product, lack of 3rd party terminals to import through etc.  FTC should never have allowed BP to buy Arco and Amoco or Exxon/Mobil or later Chev/Tex.