It's enough of a superstition to affect, of all things, the way we number the floors in buildings. This week, the New York City-based housing data and listings firm CityRealty released a list of condos in Manhattan that have a 13th floor. The company found that, out of 629 buildings with 13 or more floors, only 55 labeled the 13th floor as the 13th floor. That means only 9 percent of the condos that actually have 13th floors label them as such. The remaining 91 percent of buildings with 13th floors relabeled them. Some replaced the supposedly unlucky number with another, like 14, or 12B, or 14A. Others rejected numbers completely, using M (the 13th letter), or, if 13 is the top floor, naming it the "penthouse" instead.

As long as the 13th floor isn't named the 13th floor, it's no longer unlucky, right?

Of course not. Floors on buildings don't just disappear. (That's only possible at Wayside School, where there is no 19th story.) Yet, there are still those 574 condos in Manhattan that avoid calling the 13th floor by its actual number. And those condos vary in size, neighborhood, and price range.

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Around this time a year ago, I moved into an apartment on the 13th floor of a building that dared to label it as the 13th floor. The number didn't occur to me until after I moved in—I was mostly worried about having found the apartment on Craigslist—but even then, nothing eventful ever happened there. Sure the wi-fi cut out every now and then, but the floor wasn't haunted. My neighbors weren't disruptive. Jason Voorhees never showed up. I ended up not caring too much about living on the 13th floor.

Which, as it turns out, is the attitude most buyers and renters have, according to three brokers I tracked down who represent buildings with 13th floors. All three told me they've never had a problem renting or selling 13th-floor apartments. "I have never had a client reject a 13th-floor apartment," Alexandra Bellak, a broker with Douglas Elliman Real Estate, wrote in an email, "nor has it come up in conversation." (The grueling apartment-hunting process in Manhattan, plenty of people will tell you, is far scarier than the number 13.)

So why avoid labeling a 13th floor in the first place? CityRealty's Director of Research and Communications Gabby Warshawer tells me it's a preventative measure, in case any potential buyers or renters are superstitious. Even a slight fear of the number could stop someone from a purchase. "It's not an issue that the real-estate community is very concerned with," she admits. "But from the developers' perspective, even if there's a .01 percent chance it'll affect prices, why take a risk at all?"

Besides, she adds, taller buildings are more attractive—and lucrative—in cities like New York, and eliminating the 13th floor is an easy way to give the illusion that a building is a floor taller than it really is. It's a bit of a cheat, but it's allowed.