Discovering Urbanism uses a maps of median income changes to make the argument that city centers have prospered and suburban fringes have declined. I think that argument is too simplistic without more information--like, don't some posh downtown areas always have income growth; are the rich residents just getting richer, or is this gentrification; to what extent is this just from the housing collapse vs. a more fundamental shift, etc, but the maps do consistently show income growth in downtown areas.
Here are a few screen shots, but check D.U. for more median income shots, and visit the NYTimes link for further exploration. Gold means median income increased, blue means decrease. More intense the color, more intense the change.
|NYC -- Manhattan and environs are gold, elsewhere seems like a scattershot|
|Downtown does well-but much of declining zones are quite urban, too|
|Harder to see a strong correlation here, but note widespread decline in suburbs|