In the case of passenger cars, U.S. average fuel economy did not fall as economic theory would predict, suggesting that CAFE standards maintained the higher fuel economy of the passenger car fleet during the long period from the end of the 1979 energy crisis to the rise of gasoline prices in the early 2000s. Most recently, fuel economy has increased about one mpg from 2006 to 2007. This increase is due primarily to increased fuel efficiency of imported cars. Similarly, the law of supply and demand predicts that due to the United States' large percentage consumption of the world's oil supply, that increasing fuel economy would drive down the gasoline prices that U.S. consumers would otherwise have to pay. Reductions in petroleum demand in the United States helped create the collapse of OPEC market power in 1986.