Does fleet efficiency here mean a manufacturer's lineup measured to CAFE standards? As in: Chevy makes both the Bolt and the Silverado, so you (roughly speaking) multiple each vehicle's sales numbers x mpg and divide by total number of models? If so that would suggest that every other car would have had to get less efficient (or much bigger) in the last 15 years. I know giant trucks are a trend right now but that still doesn't seem right.