The IEA claims three factors tend to cause significant shortages in oil production — technical problems, the weather and civil unrest. Unless the Iran oil embargo has been caused by some sort of change in the global political weather, there is another. The EU ban on Iranian oil started this week, and Iran has gone so far as to admit that its economy already has been badly hurt.
The United States has tightened the vice on Iran more with sanctions set against foreign companies that do business with Iran. In a perverse sort of way, oil importers have been lucky recently. Global crude prices have fallen quickly because of slow demand from faltering world economies, a decision by OPEC to hold supplies as they are, and unexpected surpluses of crude stockpiles in some nations.
The Iran embargo was supposed to push oil prices toward the record prices set in 2008. The fact that the prediction was wrong represents one reason the economies of the U.S., China, Japan, the United Kingdom and the European Union have not stumbled worse than they already have. If Brent traded above $120 or so for several months, some fragile national economies may have buckled into depression like periods.