Well the 1967 riots didn't help much either, nor did the downward spiral in race relations in Detroit. It drove much of populace out who could move. Taxes weren't the old reason, just compounded on top of consistently corrupt administrations. https://en.wikipedia.org/wiki/1967_Detroit_riot
Looking at the actual figures, I don't think the 240K who moved out in the 00s, left because they just noticed the '67 riots. The population loss in the 70s was very small.
