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
> For some smaller population zip codes you can practically just put the name and zip code down and achieve delivery.

A 5+4 formatted ZIP code maps to just a handful of addresses. In cities with larger populations, the +4 could map to a single building, and in more sparely populated place, it might include houses on a handful of roads.

For smaller datasets, ZIP+4 might as well be a unique household identifier. I just checked a 10 million address database and 60% of entries had a unique ZIP+4, so one other bit of PII would be enough to be a 99.99% unique identifier per person.

With a geo-coded ZIP+4 database, you could locate people with a precision that's proportional to the population density of their region.

>>mywitt+ev
Yeah but we have that already in the census hierarchy. Plus you have to pay to access Zip+4 geospatial data and it changes sometime as frequently as quarterly