I don’t know. NY is a pretty complicated city. It’s really big, and the boroughs largely function as their own cities with their own income streams. Wall Street going away could really screw up Manhattan (although with the garment and jewelry districts even that effect would probably not be catastrophic) I doubt Brooklyn or Queens would really be that effected.
Good point. Detroit was essentially a single-industry economy. Once the auto makers left, there was nothing. There is still plenty of economic activity in NYC that is not related to Wall St.