Afghanistan's important resource in the past has been natural gas, which was first tapped in 1967. During the 1980s, gas sales accounted for $300 million a year in export revenues (56% of the total). About 90% of these exports went to the Soviet Union to pay for imports and debts. However, during the withdrawal of Soviet troops in 1989, the natural gas fields were capped to prevent sabotage by criminals. Gas production has dropped from a high of 8.2 million cubic metres per day in the 1980s to a low of about 600,000 cubic meters in 2001. Production of natural gas was restored during the Karzai administration in 2010.