Basic overview The 1970s See: 1970–79 world oil market chronology 1970 January 1: US Federal oil depletion allowance reduced from 27.5 to 22.0 percent. May 3: Trans-Arabian Pipeline delivery from Saudi Arabia to the Mediterranean interrupted in Syria, driving oil tanker rates to all time highs from June to December. September 4 – October 9 Libya raises posted prices and increases tax rate from 50 percent to 55 percent. Iran and Kuwait follow in November. December 9: OPEC meeting in Caracas establishes 55 percent as minimum tax rate and demands that posted prices be changed to reflect changes in foreign exchange rates. 1971 January 12: Negotiations over posted prices begin in Tehran between 6 OPEC Persian Gulf states and 22 oil companies. February 3: OPEC mandates "total embargo" against any company that rejects 55 percent tax rate. February 14: Tehran agreement signed. Companies accept 55 percent tax rate, immediate increase in posted prices, and further successive increases. February 24: Algeria nationalizes 51 percent of French oil concessions. April 2: Libya concludes five weeks of negotiations with Western oil companies in Tripoli on behalf of itself, Saudi Arabia, Algeria and Iraq. Agreement raises posted prices of oil delivered to Mediterranean from $2.55 to $3.45 per barrel; provides for a 2.5 percent annual price increase plus inflation allowance; raises tax rate from a range of 50–58 percent to 60 percent of posted price. July 31: Venezuela's Hydrocarbons Reversion Law mandates gradual transfer to government ownership of all "unexploited concession areas" by 1974 and "all their residual assets" by 1983. August 15: U.S. Government institutes Phase I price controls. Invoking the powers granted to the president by the Economic Stabilization Act of 1970, President Richard Nixon signs which orders 90-day nationwide freeze on all wages, prices, salaries and rents. September 22: OPEC directs members to negotiate price increases to offset the devaluation of the U.S. dollar. November:U.S. Phase II price controls begin. Plan is to allow for gradual 2–3 percent annual price increases, however, domestic petroleum prices remain at Phase I levels. December 5: Libya nationalizes British Petroleum concession. 1972 January 20: Six exporting countries – Abu Dhabi, Iran, Iraq, Kuwait, Qatar and Saudi Arabia – conclude ten days of meetings with Western oil companies. An agreement is reached to raise the posted price of crude by 8.49 percent to offset the loss in value of oil concessions attributable to the decline in