At the beginning of 2011, the small integrated energy company voluntarily split into a pure -
play upstream company, called Marathon Oil, and a pure - play refiner, called Marathon Petroleum Corporation.
Based on a sum - of - the - parts analysis, integrated oil
companies traded at a discount to their pure -
play competitors, whether they were pure -
play upstream, like an Anadarko or a Chesapeake, or downstream, like Valero or Tesoro.