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How many rats exist in our city?” This is one of the most commonly asked questions of pest professionals by the press around the globe. In New York City, for example, during the 1960s, local newspapers reported there was about one rat for every New Yorker. At that time, according to the U.S. Census, there were about 7 to 8 million people living in the city. Thus, 8 million rats were reportedly infesting the streets of the Big Apple, enough to make even the most laid-back New Yorker squirm.

Since then, newspapers have made periodic estimates of the number of rats per person infesting the city, ranging from one to nine depending on which paper you read and how much shock value a local reporter wishes to impart.

Of course, these estimates lack any scientific merit — or even professional guestimates — from rodent control specialists and/or city inspection agencies.

So where do such numbers originate? And why do they continue to have a life spanning decades within the press?

Pest control factoids are, no doubt, similar to any other statistic that perhaps gets a foothold via some type of un-vetted reporting — particularly from decades ago when the press was even looser with their reporting of scientific numbers than they are now. It’s fair to ask how does any urban myth gain a foothold?

THE ORIGINS. The statistic of one rat per New Yorker (a statistic cited by other major cities as well) is rooted in several theories, although no one really knows for sure when it first took on a life of its own.

One theory for the origin of the New York rats is suspected to be tied to a New York City Rat Summit that occurred during the 1970s. During the summit, one city official stated that “he believed it was possible there could be as many rats in New York as there are people.” Because the statement came from a city rodent control official, it was picked up by the city’s media as an “official estimate.” This statement was then matched to the U.S. Census count — and “voila” — there came to be about 7 to 8 million rats in New York City.

This statistic continues to be repeated as some type of “scientific formula” for estimating how many rats exist in our cities and towns. Unfortunately, the rat-per-person formula also found its way into some “semi-scientific” literature published at professional pest control meetings, university meeting guides and the like. Once such a statistic appears under the umbrella of anything within “academic circles,” it tends to become fact — and complete trust is placed in the number by the lay press.

As the statistic is cited again and again, it becomes entrenched as “fact.” From here, the now “scientific fact” becomes a staple on various TV shows, magazines, the internet and other media outlets.

It’s a safe bet that a similar pathway has occurred for many other “pest fallacies” (termites, cockroaches, bed bugs, etc.) that exist in the public sector, the press and social media.

How many rats exist in New York, or Cleveland, or Los Angeles for that matter? No one knows for sure. And for all practical purposes, this statistic is impossible to determine with any accuracy. But, in an interesting parallel, an accurate number of the New York City humans also remains unknown!

The author is one of the country’s leading “rodentologists” and a frequent speaker at industry educational events.