Re:Stop Using Zip Codes for Geospatial Analysis (2019)
by perrygeo on Friday February 07, 2025 @06:19PM
(#42978633)
> less than x distance away
zip codes don't even need to be contiguous. It's a mail delivery route, not a polygon.
There are 5 cases where the assumption is violated:
- Non-contiguous areas
- Zip codes that are a single point (some big companies get their own zip with a single mailbox, e.g. GE in Schenectady, NY is zip 12345)
- Zip codes that are a single line (highway-based delivery routes)
- Overlapping boundaries (since mail routes are linear, choosing a polygon representation is arbitrary and often not unique in space)
- Residents of some zip codes are not stationary (e.g. houseboats)
In short, asking questions about the area of a zip code is a category error - zip codes do not have a uniform representation in space. And we should be highly skeptical of any geospatial analysis that assumes polygons.
zip codes don't even need to be contiguous. It's a mail delivery route, not a polygon.
There are 5 cases where the assumption is violated:
- Non-contiguous areas
- Zip codes that are a single point (some big companies get their own zip with a single mailbox, e.g. GE in Schenectady, NY is zip 12345)
- Zip codes that are a single line (highway-based delivery routes)
- Overlapping boundaries (since mail routes are linear, choosing a polygon representation is arbitrary and often not unique in space)
- Residents of some zip codes are not stationary (e.g. houseboats)
In short, asking questions about the area of a zip code is a category error - zip codes do not have a uniform representation in space. And we should be highly skeptical of any geospatial analysis that assumes polygons.