I've seen this thing about 420,000 cats in 7 years being stated as fact on TCS now and then. I know I'm also not the first person on TCS to point out the problems with this, but I figure it can't hurt to say it again so I decided to write something about it. I wasn't sure where to put it , so it's ending up here: I just wish well-meaning, cat-loving, cat-helping people would stop repeating the debunked claim about a pair of cats left unaltered producing 420,000 cats in 7 years. , an urban legend / propaganda "statistic" that has taken on a life of its own and can backfire against cat welfare. If cats were reproducing at that rate, many countries would have TRILLIONS of homeless cats. There have been articles debunking it and major animal organizations now say they don't think it is accurate. Even HSUS ( who used to have it on their website and who were often credited as being the source) say they no longer believe it and they don't even know where the number originally came from. It's true that it is often preceded by , " theoretically" . I guess people figure that makes it "true" , if in theory one could do the math that way. But that makes it just an exercise in arithmetic, divorced from reality. A more realistic estimate in the low hundreds has been proposed based on studies of feral colonies. but that doesn't have the attractive shock value of 420,000. I understand that some people / groups say this with good intentions because they hope it will get people to spay / neuter their cats. But I don't like repeating this myth because: This very same faux statistic is used as an argument by opponents of TNR that it can't be effective since if you just miss trapping a smart queen and tom in a managed colony they'll soon have produced hundreds of thousands more cats. (The same argument would apply to trap & kill, but they sometimes think a really intensive trap and kill effort would work, or suggest other forms of mass slaughter.) If someone already dislikes free-roaming cats and hears that just a pair of them could end up creating 420,000 in 7 years, that's not likely to make them feel friendlier to the cats, and some cat haters may find in such numbers the justification for getting rid of cats by any means. As an argument for / attempt to shock people into spay/ neuter of pet cats, this figure sounds so exaggerated that it can lead people to doubt everything said by the group or individual making such a claim. More accurate numbers might actually be more effective since they're more believable . Even if the number is 100 or 200, that's still a good reason to s/n/. It makes things sound so utterly hopeless . It could lead to a defeatist attitude that it is impossible to even get to a very low kill rate in shelters... so why bother trying to make any changes in the way things have always been done? Some feral cat advocates have been trying for a while to track down where this stat came from. Barb of Feral Cats in the News wrote about it: Fable of 420,000 Cats The Feral Cat Spay Neuter Project in Seattle, WA, USA, challenged the 420,000 figure and tried to come up with a more realistic estimate. Using population data from studies of feral colonies, mathematicians arrived at a more realistic estimate of 100- 400 cats -- but that's if no adult cats die. The Feral Cat Times Feb 2006 The info is on page 2 " Dispel the Myth: 420,000 Cats?!" and on page 3. " How Many Kittens in Seven Years?" Then there was an article by the "Numbers Guy" from the WSJ about this oft-repeated number. Here is a reprint on the site of Alley Cat Allies Carl Bialik WSJ " Trying to Herd a Cat Stat" and another article a few years later in 2010 about how this (and other unproven statistics about cat predation) have persisted Christie Keith SF Gate "Damn Lies and Cat Statistics" That article includes this quote: Franny Syufy of cats.about.com admits she was one of the many advocates who repeated this number as an argument for spay/ neuter, but didn't know where it came from and hadn't thought about how it could actually be harmful 420,000 Cats in 7 Years : True or False? There are now many sources saying it's a myth , giving links or quoting the earlier articles, but unfortunately it's one of those things that is hard to get rid of. I just wish we here at TCS could stop contributing to it. But I guess I am part of the problem because I should have said something before ; not just when it's someone using this along with other false claims about feral cat population and predation, but when it is someone using it for what was probably the original intent -- promoting spay/ neuter. Yet it is certainly possible to point out that this is incorrect ,but frame that in a way that is still an argument for getting your cats altered.