Estimating downtown populations

All good suggestions. One caveat to consider is that building permits only serve as a proxy for new construction as few municipalities and counties track new completions. While this can be a good indicator of building activity during a strong housing market, it can also be very misleading during a down market. In some areas, developments that were permitted never even got past groundbreaking. And the lots are still vacant, though the building permit data says otherwise. Also, make sure that the permit data you are examining only includes new construction and excludes renovations. Next you may want to stratify the estimate of housing units by owner-occupied and rental housing. The reason being that household size and occupancy (vacancy) rates can differ by type of ownership. Which brings up the important issue of occupancy. Unless you subscribe to the Field of Dreams theory (build it and they will come), the current occupancy will be somewhat lower than the estimate of housing within the defined market area. As dated as it is, you will probably need to rely on the Census for owner-occupied housing vacancy rates, but should consult a private source, such as REIS, for rental vacancies (they have some free stuff available online).

All good suggestions. One caveat to consider is that building permits only serve as a proxy for new construction as few municipalities and counties track new completions. While this can be a good indicator of building activity during a strong housing market, it can also be very misleading during a down market. In some areas, developments that were permitted never even got past groundbreaking. And the lots are still vacant, though the building permit data says otherwise. Also, make sure that the permit data you are examining only includes new construction and excludes renovations. Next you may want to stratify the estimate of housing units by owner-occupied and rental housing. The reason being that household size and occupancy (vacancy) rates can differ by type of ownership. Which brings up the important issue of occupancy. Unless you subscribe to the Field of Dreams theory (build it and they will come), the current occupancy will be somewhat lower than the estimate of housing within the defined market area. As dated as it is, you will probably need to rely on the Census for owner-occupied housing vacancy rates, but should consult a private source, such as REIS, for rental vacancies (they have some free stuff available online).