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α: calibrated so average coauthorship-adjusted count equals average raw count
The U.S. Energy Information Administration (EIA) projects that U.S. natural gas prices will provide a substantial cost advantage over petroleum products as a transportation fuel during the next 30+ years. Although U.S. natural gas prices closely tracked those of world oil prices from the mid-1990s to early 2009, U.S. natural gas prices have been much lower relative to those for oil since early 2009. The break owes to technological change that substantially increased the supply of U.S. shale gas resources.