zlacker

>>voxada+(OP)
To put it in plain mathematical language, ZIP codes are not defined as polygons [0]. The consequence is that performing any analysis with an assumption that ZIP codes are polygons is bound to be error-prone.

0: https://manifold.net/doc/mfd8/zip_codes_are_not_areas.htm

>>jihadj+t7
Yeah. ZIP codes are sets in the abstract-dimensional space of carrier delivery points. I suppose you could think of them as lines, but definitely not polygons.

>>mholt+rf
Zip codes (in the US) are machine readable numbers a mail sorter can use to send a parcel to the right delivery truck for final delivery. In the US, they represent the hierarchy of postal centers with the most significant digit representing the primary hub for a region and the smallest number the actual post office that will be in charge of delivering the letter (or truck if you do the extended post code).

They don't represent geography at all, they represent the organizational structure of USPS.

They work by making the address on a letter almost meaningless. For some smaller population zip codes you can practically just put the name and zip code down and achieve delivery.

>>cogman+ci
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+us
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.