On Thu, Aug 18, 2016 at 3:01 PM, John F. Eldredge <j...@jfeldredge.com> wrote:
> I know I am replying to a two-month-old message, but the idea of > restrictions on entering postal codes is baffling. At least in the USA, > the Post Office encourages the use of postal codes (called Zip codes) on > mail, to expedite the delivery of mail, and used to publish large reference > books listing the postal codes for every address in a particular area. > Nowadays, they have a web site where you can enter an address, and look up > the postal code for that address. What would be the purpose of postal > codes that aren't told to the general public? Or, is it that the postal > code boundaries are restricted, but the postal code for a given address is > not restricted? There are two kinds of ZIP codes. The 9-digit postal service ZIP codes, which identify route and stop (*not* areas!), and Census zip codes (which are areas). The former gets used as part of the address commonly in the US, and is a copyrighted database subject to change at the Postal Service's whim. The fact that they want the public to know *their* idea of ZIP codes is because it makes life easier for *them.* So it kind of makes sense why they want to keep the fewest number of cooks in the kitchen to keep lines of communication with their customer base short. It just makes gathering this information a game of "Hey, what's the ZIP at this door?" The latter is used by the Census and utility companies to describe areas, and also includes places that aren't served by the postal service (and thus have some strange 3 and 4 digit entries, but no 9 digit entries used in addresses), because the whole point of Census ZIPs is to describe areas that are (hopefully, but not in all cases), at least approximately close to what the Postal Service is using for the first five digits of their ZIPs. This one is considered government data, but there's a "what's the point" factor since if there's no postal ZIP for a location, it's not usually used in the street address, either...
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