why did OPEC raise the price of oil in 1972?
In 1972, OPEC raised prices about 8 1/2% to offset the decline in the value of the U.S. dollar.
http://en.wikipedia.org/wiki/1970%E2%80%9379_world_oil_market_chronology#1972
http://en.wikipedia.org/wiki/1970%E2%80%9379_world_oil_market_chronology#1972