Data oddities

September 9th, 2023 Tagged with: technical

This week I’ve been working with a property dataset because of work with the Anti-Eviction Mapping Project. I thought to share a few funny things we’ve found since we started working with it.

Context: we are working with data from Regrid, a property data company that cleans municipal data from across the country and standardizes it into a cleaner form. Sometimes that standardization process itself produces weird things, and sometimes there are oddities left over only because the standardization could not resolve them.

  1. Some properties can be in multiple cities at once — or at least can be listed as such. We noticed this while trying to come up with proxy measures for the owner-occupied status of a given property; we noticed that the owner’s mailing address and the property address referred to the same property, but would have different cities. Weird.
  2. Many addresses aren’t parcels, many parcels might have multiple addresses, multiple buildings might exist on a single parcel, a parcel might not have a mailing address, a building very often has many mailing addresses (any multifamily building), etc. You really can’t tell whether these issues exist or how prevalent they are, or even what your assumptions about these measures are, until you make a bunch of boolean variables and then tabulate everything, and notice that some gaps you expected to be empty aren’t actually empty.
  3. Condos are such a weird case to consider. They are individually traded parcels, but they can also be rented out just like multifamily units. Should they be included in the category of “multifamily rental units” or “single-family residences”? The answer is no in both cases.
  4. Lots of corporations register under several names but have a common mailing address — a sign we take as effectively being one corporate network that owns a set of properties under different identities or faces. Looking past these facades is a key goal of our current project and of our tool Evictorbook. Here are two other interesting things about corporations and addresses:
    • Corporations, for some reason, often list the parcel address for an apartment they own as “Apt 1”, as in “123 Main Street Apt 1”. Our naive initial proxy for identifying condos, by looking for which parcels (independently bought and traded, so not traditional apartment rental units) have an apartment number, can be wrong.
  5. A surprising number of properties are owned by nonlocal owners. More about this in our report!