For the last week of December, we’re re-posting some of our favorite posts from 2012.

This morning NPR aired a segment on media stories about the “boomerang generation,” college-educated children who return to live with their parents after graduation. A widely-repeated figure is that currently 85% of recent college grads are moving back in with their parents, taken as a sign of the ongoing, and potentially long-term, consequences of the economic crisis.

Except for the part where it’s not true.

You may have heard this figure. CNN Money seems to be the first to cite it, in 2010; Time and the New York Post, among others, repeated the number:

It  continued to spread, most recently ending up in a political ad from American Crossroads that attacks President Obama.

But PolitiFact recently looked into the claim and declared it false. It supposedly came from a survey conducted by a marketing and research firm from Philadelphia. Yet as they dug further into the story, PolitiFact found many things that might make you suspicious. For instance, some people listed as employees claimed never to have worked for them, while others seem to be fictional, their photos taken from stock photo archives. One employee they did find turned out to be the company president’s dad. When they found the president, David Morrison, he said the survey was conducted “many years ago” but refused to release any information about the methodology, saying he had a non-disclosure agreement with the (unnamed) client.

But as the story of this shocking trend was reproduced, it appears reporters did not try to access the original survey to fact-check it, or surely they would have discovered at least some of these discrepancies, or the lack of any available data to back up the claim.

In contrast to the 85% figure, a Pew Center report (based on a sample of 2,048) found that for young adults aged 18-34, 39% were either currently living with their parents or had temporarily moved in with them at some point because of the economic downturn:

And importantly, of those currently living with their parents, the vast majority of 18-24 year-olds said the economy wasn’t the reason they were doing so. The study found no significant differences by education for those under 30 (42% of graduates were living at home, compared to 49% of those who never attended college), but for those 30-34, only 10% of college graduates were living at home (compared to 22% of non-college graduates).

But once the more shocking 85% figure had been cited by a mainstream news source, it was quickly reproduced in many other outlets with little fact-checking. As PolitiFact sums up,

…once a claim enters the mainstream media, it’s hard to put the genie back in the bottle. “The dynamic of trust is built with each link,” Wemple said. “It barely occurs to anybody that all those links may be built on a straw foundation.”

Gwen Sharp is an associate professor of sociology at Nevada State College. You can follow her on Twitter at @gwensharpnv.