WHAT MORE COULD THERE BE TO KNOW ABOUT ZIPS?
We introduced in the last post how ZIP codes were first introduced in the 1960s and how they were developed to help the Postal Service improve nationwide mail distribution. As we also mentioned previously, although ZIP codes were enumerated based on regional sorting facilities, geographic boundaries do not technically exist. ZIPs are actually designations identifying the point of delivery (i.e. a street address or Post Office), rather than any defined bounding region. The best example of this “placeless” designation is the US Navy, which has its own ZIP code, but no permanent location. Similarly, any high-volume recipient can have its own unique ZIP code, such as corporate headquarters, government agencies, or large institutions. ZIP codes that do represent a physical area are typically just mail delivery routes – meaning that you could have a ZIP code within another ZIP code. There are four primary types of ZIP codes: PO Box, Unique, Military, and Standard. PO boxes are located at the post office itself; unique codes refer to individual addresses; US military bases overseas have a domestic mailing address; and standard codes designate everything else (i.e. the “normal” ones). So, ZIP code boundaries can therefore be non-contiguous, undefined, or non-existent. In other words, it is fairly difficult to create a truly representative map, and the maps of ZIP codes that do exist are not comprehensive. Even more problematically, ZIP codes change – but more on that later.
SO, WHAT DOES THIS MEAN FOR DATA MAPPING?
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