

Why ZIP codes have 5 numbers – and what they each mean - altern8
http://uk.businessinsider.com/what-do-zip-codes-mean-2015-6?r=US

======
DrScump
"The ZIP+4 code was implemented when it became difficult to sort mail based
only on traditional ZIP codes, but it never quite caught on."

This is totally false. Zip+4 addressing (and, for bulk mail, presorting by
Zip+4) is _required_ for the best mail rates. Zip+4 is generally not written
in by the consumer (I do, but I'm a geek who's done mailhouse work), but it's
endemic otherwise.

I bet a fair share of any reader's outbound mail here uses zip+4 as well -
just look at the return envelopes/labels for bills, etc. that are done via
mail.

~~~
altern8
I guess "it never quite caught on" meaning that not a lot of people use it..?

