Want vacancy data? Ask the postman.

Screen shot from USPS training manual
A Postal Service training manual instructs mail carriers how to note changes in building vacancies, even under extreme circumstances. (Courtesy of U.S. Postal Service)

How many vacant homes are there in America? Lawmakers, housing researchers, even real estate developers all want to know the answer to that question, as a way of getting a handle on the lingering effects of the foreclosure crisis. But that information is hard to get. It requires on-the-ground knowledge of every street, every block, and takes constant updating to keep it accurate.

Turns out that the most accurate vacancy data available comes from an unlikely source: your postman. Who better to establish what’s happening in America’s neighborhoods than the men and women going door-to-door there every day?

“We know when new housing or apartment developments open,” reads a line from a U.S. Postal Service employee training manual. “We know too when new business parks open.”

The Postal Service employed an army of more than 307,000 letter carriers in 2013, according to the U.S. Bureau of Labor Statistics, each hoofing his or her route in rain, snow, sleet or shine. As they deliver mail, carriers act like little Census takers, noting a fresh condo tower here or a recent board-up there. That information is fed quarterly to the U.S. Department of Housing and Urban Development, which distributes it to a select group of non-profits and researchers.

But this information sometimes takes a problematic route, as the Postal Service collects it to streamline delivery and maximize revenue, not to track fluctuations in the housing market. Carriers feed data into what Postal Service insiders call “the red book,” so-called for its bright red cover. Its proper name is Address Management System Database, and it’s the agency’s master list of every last deliverable address.

That list is used to create smaller sub-lists the agency sells to private companies, to make accurate mailing labels, even to determine the best delivery routes. Each carrier has an “Edit Book” that he or she uses to note changes to the addresses on any given route as often as they occur.

The problem for researchers starts with the way the Postal Service classifies vacancies. Some empty buildings are marked as “vacant,” but others are classified as “no-stat.” A blog post from the DePaul University Institute for Housing Studies compares these two categories to the way the federal government deals with unemployment numbers. If you’re without a job but seeking work, the government considers you to be unemployed. But if you’ve been out of work so long that you’ve stopped looking, you’re no longer counted in those ranks.

The same is true for property, says the institute. Just as unemployment numbers measure workers seeking jobs, Postal Service vacancy data “measures vacant properties ‘looking for occupants’ and excludes properties that have left or have yet to enter the pool of available units.” That means “no-stat” properties, those unlikely to be occupied in the near future, are all classified the same way, whether they’re condo towers under construction or severely dilapidated houses abandoned for good.

To complicate matters further, the Postal Service includes homes that eschew residential mail delivery in favor of a P.O. Box in its no-stat numbers. Which means in the eyes of real estate observers, a house listed as no-stat may not be vacant at all.

DePaul’s housing institute added Postal Service numbers that included no-stat listings to its data portal in November, but “took that off our site after tracking it for a couple quarters,” said institute representative Tina Fassett. “It was really dependent on Postal Service oddness.”

A Postal Service spokesman did not respond to requests for information before deadline.

So how to make sense of the numbers? HUD has a few tips. An increase in the overall number of addresses “with a similar increase in no-stat addresses likely reflects new construction,” the agency suggests. No-stats in an area with a stable or reduced number of addresses likely indicates a high number of long-term vacancies.

It’s likely worth it to try to make sense of the data. “Few factors are as indicative of the strength or weakness of a neighborhood housing market as the level of long-term residential vacancy,” writes DePaul’s housing institute. And right now the Postal Service numbers are the best thing we’ve got.

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