the oil supply crises of the 1970s spurred the creation, in 1975, of the federal corporate average fuel economy (cafe) program, which required auto manufacturers to meet progressively higher fleet fuel economy targets. the next decade saw dramatic improvements in fuel economy, mostly the result of reductions in vehicle size and weight. these gains eroded somewhat after 1990 due to the growing popularity of sport utility vehicles, pickup trucks and minivans, which fall under the more lenient "light truck" cafe standard.