An oil supply disruption in OPEC member countries or in the Persian Gulf region may have unusually large effects on crude oil prices because such a disruption may escalate into wider disruptions within these volatile regions. This analysis reviews and updates several past studies to identify specific events that can be linked to oil supply shocks that remove oil production while increasing world oil prices. Using historical data, it finds that a 10% cut in world oil supplies arising from abrupt and large monthly disruptions of OPEC and Persian Gulf crude oil production correlates with a 35-43% increase in inflation-adjusted crude oil prices. The data also reveal that almost all sudden and large oil supply disruptions occurred prior to 2004, which raises some interesting issues about how to interpret the evidence from studies evaluating the impact of future oil disruptions on either prices or the economy.