zlacker

I agree that they weren't explicitly meant to represent geography, but implicitly they do, right? Are there cases where this is violated?

In other words, is it safe to assume that for entity in a zip code is less than x distance away from the closest entity in the same zip code?

>>alsodu+(OP)
it is safe to assume nothing.

Please see: https://opencagedata.com/guides/how-to-think-about-postcodes...

I write this as someone who grew up in the ZIP code 09180

>>alsodu+(OP)
It might be true, but does it help if the x varies from "on a nearby mountain" to "within a street block", and you sometimes have every habitants closer to another zip code than theirs ?

>>alsodu+(OP)
> 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.

>>alsodu+(OP)
They do provide a location with whatever error bars on it.

What they do not have is any sort of spatial consistency, they are a convenience for mail sorting. So if you start analyzing patterns across zip codes, you are pulling in information that is likely useless for or harmful to answering your question.