For almost 20 years, one of the central narratives of Canada’s relationship to Silicon Valley has been the vast national exodus of the country’s people and talent to the heart of America’s technology sector.

Since the turn of the century, it has been claimed dozens of times—by Canadian media, tech industry stakeholders and even politicians—that there are some 300,000 Canadian expatriates in the San Francisco Bay Area, just shy of the population of Canada’s 16th largest metropolitan area in Windsor, Ont.

A fascinating anthropological study could examine why so many traded Gretzky for Jello Biafra, or steamed fiddleheads for steamed burritos, or April Wine for Napa County, but that study would face one major hurdle.

There aren’t 300,000 Canadians living or working in Silicon Valley. Not even close.

And yet this “zombie statistic”—what researchers call unsubstantiated figures that suit a popular prejudice and are repeated until they are accepted as fact—has shaped the way Canada talks about its science and technology sectors, often used to inflate the urgency of claims of the so-called “brain drain” of STEM and business talent to California-based competitors.

“We have to get more talent to come back—there are 300,000 Canadians here in the Silicon Valley,” said Toronto Mayor John Tory, while on a trade mission to San Francisco in 2016.

However, according to the United States Census Bureau’s 2016 American Community Survey, there were only 132,101 foreign-born Canadians in the entire state of California.

In the nine counties that touch the San Francisco Bay, there were just 34,546 Canadians. In the smaller San Francisco-Oakland-Hayward, Calif. Metropolitan Statistical Area, only about 22,000.

A spokesperson for the U.S. Census Bureau confirmed these numbers to The Logic.

Daniel Munro, director of policy projects at the Innovation Policy Lab in the Munk School of Global Affairs and Public Policy at the University of Toronto, has written about, taught and worked on innovation policy in Canada for over a decade. He said he was baffled the first time he heard the 300,000 figure.

“It didn’t make sense to me then, nor could I understand why people didn’t step back and simply ask, ‘Is it plausible to think that one per cent of Canada’s entire population lives in just a few counties in California—and that they’re all tech workers?’” said Munro.

The week of his San Francisco trade mission, Tory repeated the 300,000 figure in an op-ed in The Globe and Mail, a newspaper that has reported the figure several times, often with cursory attributions to “current estimates” and “some estimates.”

Reuters reported the figure last year multiple times, without any citation, in its business coverage—including with specific reference to brain drain. In 2014, Reuters attributed the stat to the somewhat less cryptic “industry estimates”.

The Waterloo Region Record has advanced the claim, saying that 300,000 Canadians in the Valley work in the tech industry alone, also without citation. The Toronto Star reported that 300,000 Canadians have fled to Silicon Valley in just the two decades since the dot-com boom.

Even Canadaland, the media watchdog which often criticizes Canadian publications for their errors, made the zombie statistic a central point of urgency in a 2016 podcast episode on the country’s tech industry. “We have a problem in Canada when it comes to our tech sector,” said host Jesse Brown. “We have incredible talent that comes out of Waterloo and elsewhere, but something like 300,000 Canadians have taken their talent with them to Silicon Valley.”

From the Financial Post to BetaKit to this very publication, which fell for the zombie stat at its launch, the figure has circulated unchecked for at least 19 years. As far back as April 8, 1999, the Financial Post reported, “By some estimates, about 300,000 Canadians have moved to the Silicon Valley area and another 600,000 are located in and around Los Angeles.” A year later, the Globe reported 300,000 Canadians live in Northern California “a population as big as Saskatoon, Sask.”

To boot, Canadian diplomats have helped circulate the unsubstantiated number, with the country’s San Francisco consulate telling Dow Jones in 2010 that 250,000 to 300,000 Canadians lived in northern California.

Munro, who is also a researcher in residence at Actua, a national charity focused on STEM education, points out that the zombie stat has been used to argue for Canadian policy: “It’s absurd. The troubling thing is how it’s used to raise alarm about a brain drain and how Canada needs to do more to retain talent. Those are legitimate concerns, but the scale of the issue—if there is an issue—is totally off-base.”

The Migration Policy Institute (MPI), a Washington, D.C.-based think tank that studies the global movement of peoples, told The Logic that the Census Bureau data is the most reliable count for determining the number of foreign citizens in the United States.

The Embassy of Canada in Washington, D.C., the country’s main diplomatic mission to the U.S., concurred, saying, “Our best advice would be to trust an American census.”

California is by no means unattractive to Canadians—on its website, the MPI notes that 16 per cent of the 783,000 Canadians who lived in the U.S. as of 2016 had settled there, the most of any state. It also lists the San Francisco-Oakland-Hayward Metropolitan area as having the eighth-largest Canadian population among U.S. metro areas.

Michelle Mittelstadt, director of communications at MPI, said exaggerations about migration data are common. Foreign governments, for instance, may inflate the number of nationals in the U.S. by counting U.S.-born children of immigrants.

“Or one statistic takes hold and is used endlessly, year after year, regardless of changing conditions,” she said. That’s happened with the count of undocumented Irish immigrants in the U.S., which has rhetorically held steady at 50,000 for years.

“No one appears to remember where that original estimate was derived, yet the number lives on year after year,” said Mittelstadt.

Munro notes that even if Canadian officials—or whoever came up with the Valley zombie statistic—did tally the children of expatriates and a few other add-on factors, it would remain nearly impossible to get to 300,000 people.

“Heck, if [the U.S. Census Bureau] numbers are even 100 per cent off,” he said, “you’re still looking at 50,000 to 60,000 of all types of residents.”

Follow The Logic on Facebook, LinkedIn and Twitter (@the_logic), and sign up for the Daily Briefing newsletter.