The United States was so dependent on foreign oil that by 2008, it imported two-thirds of what the country's refineries needed to produce enough gasoline, diesel and other petroleum products to meet the country's needs.
But recently, the federal Energy Information Administration reported that in 2010, imports had fallen far more than many realized -- to 49 percent of the country's needs.
Part of the big drop resulted from the federal agency's using a different measurement -- net petroleum imports -- widely viewed as a more accurate way to judge overall dependence on foreign petroleum. The figure counts imports of crude oil and of refined petroleum products such as gasoline and diesel, but it also subtracts exports of U.S. petroleum products, which have been growing.
The country recently stopped being a net importer of petroleum products for the first time since at least 1973, as the country's refiners sold more gasoline and other end products to other countries.
A second factor is simply lower demand for petroleum products, in large part a result of the sour economy but also helped by more efficient cars.
And on the supply side, U.S. oil production, after languishing for years, is on the upswing.
One example is North Dakota. Perhaps within a year, the state is expected to supply more oil for domestic use than the 1.1 million barrels a day that Saudi Arabia now exports to the United States.