Concentration levels are larger in
deep water than for the Gulf as a whole, but these levels have been declining over time. The implied
long-run levels of concentration are generally smaller than the cutoff level of .15, which places the
levels in the “unconcentrated” category. These results cover a wide range of market conditions,
including periods of recession, booms and busts in oil markets, technological innovation and big
mergers. Finally, the evidence suggests concentration is falling over time, particularly in deep water