When we look at some population numbers, a different story begins to emerge. Yes, Detroit has lost quite a bit of population, dropping from a peak of 1.85M in 1950 to .77M today. The first thing we should know though, is that most of the automotive and manufacturing plants moved out of Detroit. That's right. They're in the suburbs: Dearborn, Livonia, Birmingham, etc.
So based on the premise that the auto industry killed Detroit, shouldn't the metropolitan area have suffered as well?
It hasn't. Not at all. While Detroit fell from 1.85M to .77M people, the region has grown to nearly 5M, up from 3.3M since 1950. Even when you look at the various aerials of the aerials on google earth, it is only within Detroit proper that areas are bombed out. Neighborhoods in immediately adjacent Dearborn are full and stable, nary a missing "tooth" to be found.
Between that period on a county by county basis, the Detroit MSA is in five counties, from the 1960 to 1990 census only Wayne County lost population:
County: 2000 - 2010 (+/-) %
Wayne (Detroit): 2.6M - 2.1M (-.5) -19%
Oakland: .69 - 1.08 (+.39) 56%
Macomb: .4 - .7 (+.3) 75%
Washtenaw: .17 - .28 (+.11) 65%
Monrow: .10 - .13 (+.03) 30%
While Detroit proper has continued to lose population since including a staggering 25% between 2000 and 2010, the suburbs have held relatively steady or grown, particularly the bleeding exurban edge.