http://online.wsj.com/article/SB10001424052702303382004579131460420...

"Most recent is the development of "tight oil," the spinoff from shale gas, which has increased U.S. oil output by more than 50% since 2008. This boom in domestic output increases energy supply, and combined with shale gas has a much wider economic impact in jobs, investment and household income. As these tight-oil supplies increase, and as the U.S. auto fleet becomes more efficient, oil imports have declined. Imports reached 60% of domestic consumption in 2005, but they are now down to 35%—the same level as in 1973."