Professor Simester and his colleagues then compared the buying habits of households before and after they moved, to see if transitioning to a new area affected them. It didn’t. Even when harbingers moved to a neighborhood of nonharbingers, their disaster-prone tendencies persisted. They didn’t rub off on their neighbors, either. “If you’re not a harbinger and you accidentally move into a harbinger ZIP code, you don’t start buying strange products,” Professor Tucker explains.

This remarkable finding suggests that the clustering of harbingers at the ZIP code level is a result not of social learning but of water seeking its own level. Evidently, the same irregular drumbeat that harbingers march to while browsing the aisles of supermarkets and private label clothing stores also guides their decisions about where to live, leading them to the same neighborhoods.

And as with their tastes in soda and jeans, these decisions have a predictably gloomy result: Property values in harbinger ZIP codes consistently underperform the broader market, according to an analysis of changes in housing prices across more than 4,000 ZIP codes over 12 years.

Being a dowsing rod for disappointments, moreover, appears to be a curiously stable attribute, a “sticky” trait that is transported but not transmitted and doesn’t bow to shifting social norms. “It’s not a contagious thing,” Professor Tucker says. “It’s an inherent characteristic.”

But what exactly is that characteristic? Who are the harbingers?

Attempts to characterize these people have borne little fruit. The harbingers are slightly more concentrated on the West Coast and in nonurban areas, demographic data has shown, but other than that they exhibit no clear geographical pattern. They may be a little wealthier than average and have bigger families, although the evidence for that is open to doubt. They shop at warehouse clubs like BJ’s and Costco — but then, who doesn’t? And they’re big on variety: Harbingers buy a wide assortment of brands but make fewer repeat purchases than the average consumer, which may explain why demand from harbingers alone isn’t enough to sustain the products they acquire.

That’s the closest thing to a composite sketch researchers have been able to draw, and admittedly it leaves many questions unanswered. Perhaps, Professor Tucker suggests, harbingers are simply on a different wavelength from the rest of us. “I think what we’re picking up on is that there are just some people who, for whatever reason, have consistently nonmajority tastes,” she says, noting that in addition to buying short-lived products, harbingers buy a lot of niche items. “They like that odd house. That political candidate everyone else finds off-putting. They like Watermelon Oreos.”

Even if we aren’t sure what makes harbingers tick, we can still learn from them. For one thing, they may help us understand why many products that debut to strong sales and positive customer feedback wind up tanking, a problem that has long confounded marketers. “If you want to predict which products are going to be successful, you don’t just want to look at total sales,” Professor Simester says. “Look at who’s buying.”