LEILA FADEL, HOST:
The holidays were busy for mail carriers because we were busy sending packages with a familiar five-digit code. Our Planet Money team got curious, where did ZIP codes come from? Here's reporter Sally Helm.
SALLY HELM, BYLINE: Most of us use ZIP codes without even thinking about them. But when they were first introduced in the 1960s, the public was not convinced. So the post office pulled out all the stops in advertisements and PSAs and songs.
(SOUNDBITE OF ARCHIVED RECORDING)
ETHEL MERMAN: (Singing) Welcome the ZIP code. Learn it today. Send your mail out to the five-digit way.
HELM: That's singer Ethel Merman advertising this mail revolution. People had to learn what the ZIP code was, starting with the name. Here's Lynn Heidelbaugh of the Smithsonian's National Postal Museum.
LYNN HEIDELBAUGH: It's just an acronym. It's zone improvement plan.
HELM: It definitely sounds like one of those acronyms where they came up with what they wanted it to say, and then they were like, what can we fill in (laughter)?
HEIDELBAUGH: Exactly. I don't think it was just serendipity.
HELM: No, no. Everything about the ZIP code was created very intentionally to help an overstressed post office sort and deliver the mail. Mail sorting was still happening by hand, and the post office wanted to prepare for an automated future.
HEIDELBAUGH: Ushering in this modern 20th century.
HELM: OK, so there's a big push like new, new, new - machines, machines. That's the feeling?
HEIDELBAUGH: Exactly, and also economize at the same time.
HELM: So picture a map of the U.S. The post office divided it into 10 big sections and numbered those zero through nine. That's the first number in the ZIP code. The next two numbers point to a particular processing center, and the last two are for a particular post office or neighborhood. It's a simple but powerful way to wrangle a huge volume of letters and packages. But after it's invented, something happens. People realize they can use ZIP codes for other purposes, like advertisers who want to do targeted marketing, which doesn't always work perfectly because ZIP codes define postal roots. They weren't created by pulling out a map and drawing a circle around a certain area. So if you try to use them to analyze space in the real world, it's easy to make mistakes, like thinking someone lives in one ZIP code when they actually live in another. Here's geographer Tony Grubesic of the University of California at Riverside.
TONY GRUBESIC: The stakes can be very small. You know, you send your packet of coupons to the wrong neighborhood or to the wrong set of households. That's not a fatal error.
HELM: But the stakes can also be high. A lot of public health data is organized by ZIP code. Insurance companies sometimes use ZIP codes to help inform coverage decisions. So it's important that governments and insurers are using good location data. Geographers like Grubesic often prefer precise methods like geocoding, and they warn researchers should be really careful with ZIP codes.
GRUBESIC: I would strongly encourage people just to stick with the mail when it comes to ZIP codes and leave those be for any kind of real socioeconomic or public health analysis.
HELM: For the mail, though, ZIP codes are now indispensable, just like the post office told us they'd be back in the 1960s.
(SOUNDBITE OF ARCHIVED RECORDING)
UNIDENTIFIED SINGER: (Singing) Wherever my true love may take it to be, now ZIP code will find her for me.
HELM: For NPR news, I'm Sally Helm. Transcript provided by NPR, Copyright NPR.
NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.
