Yesterday, I reported that the oft-cited, debate-driving statistic that Americans use 500 million plastic straws a day was the product of a 9-year-old's guesstimations. Despite those shaky factual foundations, the 500 million figure has quickly spread, virus-like, across the media landscape and even into our shops and schools.

Visitors to the D.C. tea house Teaism—just a short walk from Reason's D.C. office—will be confronted with the questionable fact on a small poster adorning the restaurant's single-use straw dispenser, replete with a picture of a cute sea turtle. Meanwhile, impressionable children at the Mount Vernon Community School in nearby Alexandria, Virginia, are coming home with "Straw Wars" handouts citing the same dubious figure.

It's easy to understand how the school could have been led astray, given how ubiquitous this claim is in the media. Please see below for a list of just a few of the news outlets that have cited this "fact"—or otherwise quoted people saying it without any critical pushback—in their reporting:

Activist groups are also quick to promote the claim. Among them:

And of course government officials have embraced the number too. The National Park Service has touted it. So has California Assemblyman Ian Calderon. It's in the text of a Hawaii bill that would ban the distribution of plastic straws in the state.

It's sad that so many outlets are treating the rigorous survey work of an elementary school student as the statistic about plastic straw use. But it's not very surprising. Attempts to ban plastic straws—or indeed any plastic product—have as much to do with signaling your environmentalist bona fides as they do with actually cleaning up the oceans or saving the planet. So people pushing the claim have little incentive to investigate it. And the media have every incentive to hype the impact of a phenomenon they're covering.

Let this serve as a reminder: A statistic's popularity does not prove its accuracy.