"Energy policy has been a recurring issue for Congress since the first major crises in the 1970s. As an aid in policymaking, this report presents a current and historical view of the supply and consumption of various forms of energy. The historical trends show petroleum as the major source of primary energy, rising from about 38% in 1950 to 45% in 1975, and then declining to about 40% in response to the energy crises of the 1970s. Significantly, the transportation sector continues to be almost completely dependent on petroleum, mostly gasoline. Oil prices, which had been low and stable throughout the 1990s, resumed the volatility they had shown in the 1970s and early 1980s. Starting in 2004, perceptions of impending inability of the industry to meet increasing world demand led to rapid increases in the prices of oil and gasoline. The continuing high prices stimulated development of nonconventional oil resources, first in Canadian oil sands, then in the United States in shale deposits. U.S. oil production, which had apparently peaked, showed a dramatic increase starting in 2009. U.S. imports of oil have also been decreasing over the same time period, and there are calls to allow more exports. Natural gas followed a long-term pattern of U.S. consumption similar to that of oil, at a lower level. Its share of total energy increased from about 17% in 1950 to more than 30% in 1970, then declined to about 20%. Recent developments of large deposits of shale gas in the United States have increased the outlook for U.S. natural gas supply and consumption in the near future, and imports have almost disappeared. The United States is projected to be a net natural gas exporter by 2018."
CRS Report for Congress, R40187