Ford moved 105,932 Mustangs in the United States during 2016, finishing well clear of both the Chevrolet Camaro and the Dodge Challenger and extending a winning streak that had already run several years. The interesting part is not the margin but what was happening underneath it, because Chevrolet had just launched an all-new Camaro and Dodge was selling a car whose basic architecture dated to 2008. Here is what actually drove those numbers.