I'd like to see if any of these results and conclusions change if you take into account the total tax basis for suburbanites (income tax, sales tax spent in the cities they don't live in, etc.) versus the relatively less well off inner city urbanites. Not all areas are the same, but in places like the Bay Area, a lot of the high income earners move out to the suburbs (think Palo Alto, Pleasanton, Walnut Creek, etc.).

To add, a lot of the economic activities in downtown areas are by workers and customers who live in the suburbs and commute into town. I don't believe that was taken into account.