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Attack of the 12-Foot Rats: Why Bad Math Runs Rampant

Media Mind

Tamar Wilner

June 15, 2016

When I first saw the meme, my Facebook friends were already debunking it.

The graphic states that $1.3 billion divided by 300 million is $4.33 million. If you have a calculator at hand (there’s one called Google) or remember your scientific notation, this takes just seconds to disprove. Divide that record-setting Powerball jackpot among all Americans, and we’d each get just $4.33.

But at the time of this writing, this Facebook post had racked up 912,000 likes and over 1.3 million shares. It seems that many, many people didn’t do the math.

One group that doesn’t do the math nearly often enough: journalists. Take this reporter’s tale, told to, about an insurgence of urban rats:

“I interviewed an exterminator who told me these rats were huge, but mistakenly gave me their length in centimeters rather than millimeters. Being notoriously bad at math, I wrote it verbatim and none of our proofreaders caught it.

“It’s a wonder I didn’t start a riot with news of what would have been 12-foot rats running rampant across the city.”

Somehow, while mathematical errors are among the easiest types to debunk, they’re also terrifically easy to disseminate. Why does bad math spread so easily? And why don’t journalists stop to check their math more often?

Just imagine how big that cheese must be.
AlexK100 via Wikimedia Commons.

Innumerate—or Just Anxious?

The most obvious answer is “people are bad at math.” And there is some truth to this: 61 percent of U.S. residents have Level 2 numeracy or below, on a scale of 1–5, according to the Program for the International Assessment of Adult Competencies (PIAAC), a large-scale study by the Organization for Economic Cooperation and Development (OECD). That means a majority of Americans struggle with simple problems such as reading line graphs and thermometers.

The U.S. had one of the lowest numeracy levels of the twenty-two countries surveyed, but the others didn’t do too hot either: across the sample, 53 percent of respondents achieved Level 2 or below.

But this is only a partial explanation. There’s also the issue of how good people think they are at math. Our society seems to encourage people to proclaim “I can’t do math to save my life!”—a claim they wouldn’t dare make about reading. And not surprisingly, low math confidence goes hand-in-hand with high math anxiety.1

Math anxiety affects women disproportionately,2 partially through the psychological process known as stereotype threat. An oft-cited study found that the two sexes performed equally well on a math test—but when women were reminded of the stereotype that they’re worse at math, their scores fell considerably.3 It’s likely that this stereotype threat further pressures women to avoid math.

Worryingly, math anxiety is also pretty prevalent among journalists. A study of 148 editorial staffers at one newspaper found that the journalists’ math skills weren’t great—on average, they missed nearly a third of basic, junior-high level questions.4 But their math confidence was even worse, and was low even among the best performers on the test.

9 + 7 = 39

It’s not just journalists. Because of math anxiety, many of us shy away from even the simplest of math problems. And studies have consistently shown that high math-anxiety people perform worse on math tasks.5 This seems to be true even when you control for math ability.6,7

A particularly interesting study found that highly math-anxious individuals performed badly on a test of “number sense,” which asked them to judge if equations were true or false. As the statements became increasingly implausible (such as 9 + 7 = 39), the math-anxious participants actually made more errors.8

This chimes well with my observations. As a volunteer tutor for a GED-prep program, I’ve noticed how rarely students stop to ask themselves whether a math answer makes sense. My husband, a university physics professor, has observed the same phenomenon. Now I have an inkling why.

Mathiness = Truthiness

Another reason why we don’t fact-check math: there’s a tendency to ascribe truthiness to a claim with numbers in it. In one experiment, Mérola and Hitt found that low-numeracy individuals were almost as persuaded by irrelevant data as they were by relevant data.9 For high-numeracy individuals, relevance was much more persuasive.

What’s more, for the high-numeracy individuals, it didn’t make any difference which political party was trying to persuade them. But for the low-numeracy participants, political party seemed to make all the difference: completely irrelevant data from their own party swayed them, while pertinent data from the opposite party did not.

In essence, the authors say, these participants were not so much persuaded by argument as “impressed by a barrage of figures.” We might then hypothesize that low-numeracy individuals are more likely to pass on bad-math memes—not just because they’re less likely to understand the math, but because they find the very presence of figures impressive and persuasive.

Those who juggle numbers with ease shouldn’t get too complacent, however. Kahan, Peters, Dawson, and Slovic found that the more numerate people are, the more polarized they are when evaluating a data-fueled political argument.10 The authors theorize that highly numerate people use their abilities “opportunistically.” These participants settled for the wrong answer—the one that seemed true at first blush—if that supported their political affiliation. But when their outlook was threatened, they switched on their more advanced math skills and discovered the correct answer.

Check One, Check Two

Finally, I think there’s some additional blame to lay at journalists’ feet. While the same anti-math mindset tends to afflict both readers and writers, and while we might aspire to a culture in which more social media users fact-check their posts, journalists have a professional responsibility to check the math in their stories.

Too often, that doesn’t happen. Take this contention by MSNBC’s Chris Matthews, broadcast at 2:21 pm PST on January 12, 2012:

By 7:21 pm, the figures were rather different:

Does the federal government employ 4,443 people, or 4.44 million? Was the increase thirteen people or 13,000? Never mind, somehow it didn’t stand in the way of Matthews making his point. (Nor did he feel compelled to acknowledge the error—it’s a wonder what overdubbing and graphics can do.)11

The avoidance of this fact-checking responsibility—whether it’s driven by carelessness, lack of time, or even debilitating math anxiety—represents a professional and ethical failure. As journalist Craig Silverman states, “We’re not a fancy retweeting service for companies and governments—our role is to verify information.” That even goes for the seemingly unassailable figures put out by respected non-profits. When it comes to checking numbers, no cow is sacred.

Watching Our Language

There is, however, reason to be hopeful. The rise of data journalism has revealed a class of news practitioners who are passionate about getting the numbers right and urge the end of the “I suck at math” excuse. Training organizations offer “math for journalists” classes, too.

It’s time to start spreading this message more widely. Math is doable. And it’s essential. We need it to understand everything from politics to finance, sports to health. So if you must claim to be “bad at math,” at the very least, say it under your breath. Children may be listening.


  1. Ashcraft, M.H. 2002. Math anxiety: Personal, educational, and cognitive consequences. Current Directions in Psychological Science 11(5): 181–185. Available online at
  2. Ibid.
  3. Spencer, S.J., C.M. Steele, and D.M. Quinn. 1999. Stereotype threat and women’s math performance. Journal of Experimental Social Psychology 35(1): 4–28. Available online at
  4. Maier, S.R. 2003. Numeracy in the newsroom: A case study of mathematical competence and confidence. Journalism & Mass Communication Quarterly 80(4): 921–936.
  5. Ho, H.-Z., D. Senturk, A.G. Lam, et al. 2000. The affective and cognitive dimensions of math anxiety: A cross-national study. Journal for Research in Mathematics Education 31(3): 362–379.
  6. Ashcraft, as above.
  7. Silk, K.J., and R.L. Parrott. 2014. Math anxiety and exposure to statistics in messages about genetically modified foods: Effects of numeracy, math self-efficacy, and form of presentation. Journal of Health Communication 19(7): 838–52. Available online at
  8. Faust, M.W., M.H. Ashcraft, and D.E. Fleck. 1996. Mathematics anxiety effects in simple and complex addition. Mathematical Cognition 2(1): 25–62.
  9. Mérola, V., and M.P. Hitt. 2016. Numeracy and the persuasive effect of policy information and party cues. Public Opinion Quarterly 80(2): 554–562. Available online at
  10. Kahan, D.M., E. Peters, E.C. Dawson, et al. 2013. Motivated numeracy and enlightened self-government. Yale Law School, Public Law Working Paper No. 307. Retrieved from
  11. Credit due to NewsBusters for finding this error, and h/t to conquermaths for alerting me to it. Both clips verified using the Internet Archive.

Tamar Wilner

Tamar Wilner's photo

Tamar Wilner is a Dallas-based journalist, researcher, and communications graduate student, specializing in the study of misinformation and science communication. She's written and consulted for the Columbia Journalism Review,, and American Press Institute, and she co-created Post Facto, a game that teaches people how to fact check stories in their social media feeds. You can find her at and on Twitter at @tamarwilner.