The recent meeting of OPEC provides an opportunity to understand the mysteries of the global oil market. As expected, OPEC decided not to cut its oil production. Barring unanticipated developments, prices will drop, says oil analyst Larry Goldstein. Potential oil supply, including drawdowns from bloated inventories, exceeds demand. Goldstein rightly cautions, however, that no one knows where prices will settle.

Oil's dramatic price changes seem baffling. In mid-2014, crude prices averaged around $100 a barrel; now, they're gyrating between $50 and $60. Over the same period, U.S. gasoline prices have dipped from more than $3.50 a gallon (3.8 liters) to around $2.50. With the world economy slowly recovering, why have prices collapsed?

The standard explanation comes in two parts.