The nine digit ZIP Code is utter nonsense.
The original proposal for the Zone Identification Postal Code had merit. With just five digits, potentially a hundred thousand discrete locations, you can get a letter or a package to the nearest post office.
For decades, on the outsides of my correspondence, I have put only my name (or usually just my initials), my street address, and the five digits. Never a problem. For a couple of months in 1976 or ‘77 I sent it out with addressees’ explicit city and state lacking, as those data are supposedly subsumed by the ZIP Code. But, because the Post Office employs human beings (who are idiots) they couldn’t figure out how to read their own allegedly superior system, yet they somehow managed to get it back to me, marked “undeliverable”.
Insofar as the USPS can’t be relied on to take itself seriously, and those extra four digits only allow for ten thousand locations within each Zone, it is clearly inadequate to the urban scene, and irrelevant to the rural.
190208