Using data on 61 oil companies from 2001-09, we examine the evolution of revenue efficiency of National Oil Companies (NOCs) and shareholder-owned oil companies (SOCs). We find that NOCs generally are less efficient than SOCs, but their efficiency increased faster over the last decade. We also find evidence that partial privatizations increase operational efficiency, and (weaker) evidence that mergers and acquisitions during the decade tended to increase the efficiency of the merging firms. Finally, we find evidence that much of the inefficiency of NOCs is consistent with the hypothesis that government ownership leads to different firm objectives.