Here’s how we identified more than 11,000 empty, rentable homes in New Orleans:

On September 15, New Orleans Mayor Ray Nagin announced that residents in areas with the following zip codes would be allowed to return to their neighborhoods, most of which escaped serious damage from Hurricane Katrina: 70131, 70114, 70118, 70115, 70130, 70113, 70112 and 70116. (He has since temporarily suspended the repopulation plan.)

At least six of New Orleans’ twelve districts have neighborhoods that fall within these zip codes. The Greater New Orleans Community Data Center provides the latest Census data for each of the city’s seventy-three neighborhoods. Looking only at those that fall within the zip codes deemed habitable by the mayor, we calculated each neighborhood’s number of vacant housing units by multiplying that neighborhood’s total number of housing units by its vacancy rate:

Adding them all up equals 11,617 vacant housing units in New Orleans’ dry zones. When we include neighboring Jefferson Parish to the west of the city, the total jumps to 23,267.

Some neighborhoods fall within more than one zip code area. In those cases where a neighborhood included on the Mayor’s list also has a Zip Code that is not, that neighborhood was excluded in its entirety.

The number of available homes in the New Orleans area may therefore be higher than we have estimated. One exception was made with the Central City neighborhood in the Central/Garden District.

This neighborhood shares four zip codes, one of which was not on the Mayor’s list. But this zone represents about one-quarter of the area, and its inclusion is more than offset by the many other vacant homes in those other half-flooded, half-dry neighborhoods that we have left out of our total.