U.S. auto buyers are used to downsizing. It came in the mid-1970s after the first oil shock, and it's back again right now with the shift from SUVs to crossovers. But in Europe it's pretty much an alien concept. For decades they've run a simple size escalator. Every model gets slightly bigger with each successive generation. That way, every buyer, on replacing his car with the same nameplate, progresses through life in a series of bigger, richer, pricier automobiles. Then after about three generations, there's room to slot in a fresh one at the bottom. So behold the BMW 1 Series, a car that kind of does the job of (deep breath) the 3 Series before the 3 Series before today's 3 Series.