New York Times: IT wasn’t a particular look or style that dominated the conversations of designers at the 2010 Detroit auto show, and it wasn’t a buzzword like retro or kinetic or flame-surfaced. It was the shadow of a number: 35.5. That number is not the median age of the United States population, which is 36.7 years and rising, according to the government. Rather, 35.5 is miles per gallon, the required fleet average fuel economy that automakers must achieve in 2016 under the Obama administration’s …