OPEC, excluding Iran, made $982 billion from exporting oil in 2012, the most in 38 years of data, the U.S. Energy Information Administration reported Monday. It forecast that sales will drop in 2013 and 2014.

Net oil-export revenue by the 12-member organization climbed 5.4 percent last year from 2011, according to the EIA, the Energy Department’s statistical arm. Sales will tumble by 4.3 percent to $940 billion this year and by 3.9 percent to $903 billion next year, the agency said.

Demand for OPEC’s crude will slip by 300,000 barrels a day next year to 29.6 million barrels, or 2.6 percent less than the group is pumping now, OPEC said July 10 in its first set of forecasts for 2013. Exports to North America face growing competition from a surge in production from shale basins in the U.S. and Canada. U.S. crude output reached 7.35 million barrels a day at the end of April, up 17 percent from a year earlier.

Saudi Arabia, OPEC’s largest producer, earned 32 percent of the 2012 total, or $311 billion, the EIA said.

The agency excluded Iran, OPEC’s second-biggest producer a year ago which is now in sixth place as sanctions aimed at stopping the Islamic republic’s nuclear program have hindered its ability to export crude. A European Union ban on the purchase, transport, financing and insurance of Iranian oil went into effect July 1, 2012.

Iran Sanctions

Iran wasn’t included because of “the difficulties associated with estimating Iran’s earnings, including its inability to receive payments and possible price discounts Iran offers its existing customers,” the EIA said.

After adjusting for inflation with 2005 dollars as a constant, OPEC’s revenue increased by 3.2 percent to $835 billion in 2012, the EIA said.

According to a monthly oil-market report from the Paris- based International Energy Agency earlier this month, OPEC members pumped 30.61 million barrels a day in June compared with 30.98 million barrels in May. That level exceeds a target of 30 million that the group reaffirmed at its last meeting on May 31.