As any die-hard soccer fan will tell you, the biggest “football” matchup of 2015 wasn’t that game in February between the New England Patriots and the Seattle Seahawks. It was Sunday’s El Clasico, the game played at least a couple of times each year between FC Barcelona — featuring talented footballer Lionel Messi — and its archrival Real Madrid CF — featuring talented footballer Cristiano Ronaldo.

If you don’t understand what a big deal it is for these two to face off, there may be no better way to explain than to say that for much of the world, they’re basically real-life superheroes:

If you watched last weekend’s English-language broadcast of El Clasico on beIN Sports, you were likely treated to some of announcer Ray Hudson’s classic rhetoric — at one point, he called an unsuccessful Neymar finish “as sharp as a bag of wet mice.” (Whatever that means.)

But what caught my attention was Hudson’s claim that not only were “the Martians” watching the battle at Camp Nou — so were over a billion humans.

While that viewership estimate is floated around quite commonly, where it comes from is unclear. No reasonable sources appear to make the claim, but the more reasonable-sounding viewership of 400 million suggested by Wikipedia is used by a number of credible-sounding publications such as Forbes, CNN, the BBC, the Daily Mail and even FiveThirtyEight parent company ESPN. While not quite as unlikely as 1 in every 7 people on Earth being tuned into a regular-season Spanish football contest, this 400 million number would merely be several times larger than the number of viewers of the Super Bowl (which averages over 100 million). That may sound more reasonable, considering that this is one of the premier soccer matches of the year and that plenty of claims are made about regular-season soccer matches outdrawing the premier sporting event in the U.S.

But virtually all such claims are bogus. This is what qualifies as Urban Legend in the 21st century: statistical misinterpretation (or misrepresentation) that gets repeated over and over as fact.

First, let’s look at how improbable even a figure of 400 million would be. It’s impossible to know exactly how many people are watching globally because that would require us to know how many people watched in each country — something that international networks don’t always release. And when they do, it’s not always reliable. So I’m going to start with Internet searches as a proxy for interest. We don’t need to know exact numbers, only if something like 400 million viewers is within the realm of possibility.

Let’s start by comparing El Clasico to the World Cup, the premier soccer event in, well, the world. It comes around once every four years and is broadcast in virtually every nation. Here’s how the World Cup stacks up to “El Clasico” in terms of Internet search interest:

Unsurprisingly, El Clasico is barely a blip compared with the absolute fever that accompanies the World Cup. Yet what kind of viewership did the World Cup wrangle? Although international TV viewership is never easy to pin down, it’s more reliable for the World Cup because, get this, it used to be so unreliable. After FIFA got its hand caught in the cookie jar with wildly implausible estimates, it began using audited results. As such, 2014 numbers may not even be finalized yet, but viewership numbers for the 2010 World Cup final between Spain and the Netherlands are available and give some meaningful breakdowns:

FIFA gives a topline number of 909.6 million viewers who watched at least one minute of the game at any point.

FIFA says 619.7 million people watched at least 20 consecutive minutes.

FIFA says the game had 530.9 million viewers on average.

Note that for comparison purposes, numbers reported for the Super Bowl are usually given only in terms of average viewers in the United States.

Maybe this isn’t a fair comparison because “El Clasico” is a more narrow term. But surely an event that gathers 80 percent of the audience of the World Cup final a few times a year would at least spike in search queries every once in awhile. Or, to put it another way, an event that supposedly has 3 to 4 times the viewership of the Super Bowl would surely see either itself, or at least its participants, spike beyond Super Bowl levels:

But no. While Barcelona and Real Madrid maintain high levels of interest and do in fact spike around El Clasico time (though they spike less than when they make deep runs in the UEFA Champions League), they don’t ever even exceed (much less quadruple) the Super Bowl at its peak.

So what’s a more reasonable estimate of El Clasico viewership? I’ll get there. But first, let’s identify what’s really going on here.

Trying to follow source to source to source to find out where this misinformation comes from is like a crazy clickventure. By my research, most, if not all, roads lead back to a 2012 presentation by Mediapro, the company that produces TV coverage for El Clasico. In particular, Mediapro (according to some contemporary accounts of this event) bragged about its distribution network and apparently claimed that the game would be available to “a potential audience” of over 400 million people in more than 30 countries.

Yet, this story on the FC Barcelona website claims that there will be an “expected audience of about 400 million viewers.” That phrase “expected audience” is, as you may have guessed, highly deceptive. If “potential audience” and “actual audience” were the same thing, Firefly would have been the biggest hit ever (tied with every other show on major network television). Yet that 400 million number has stuck like glue. Bizarrely, it hasn’t even changed with circumstances: For example, this 2014 article describes how Mediapro is now capable of showing the game in over 100 different countries yet still cites the same 400 million audience figure.

And this exact “potential” versus “actual” sleight of hand is nothing new. The English Premier League encouraged similar conclusions about the popularity of its games that have been easily debunked. Indeed, it’s the exact same category of claim sometimes made (also incorrectly) on behalf of the NFL and the Super Bowl.

My colleague Carl Bialik has documented similar issues not only with claims regarding sporting events — like U.S. vs. China basketball in Beijing (which claimed over a billion viewers but probably had more like 100 million) — but also with TV powerhouses like the Oscars (which used to claim that over a billion people watched) and special events like Live Earth (Al Gore’s environmental awareness concert that claimed an audience of over 2 billion).

So let’s throw that 400 million number out the window. What’s a more reasonable estimate?

Since the United States has the most transparent ratings information, let’s start there. According to beIN Sports (the cable network that has North American broadcasting rights to El Clasico), the marquee Spanish match garnered about 1.3 million viewers in Spanish and 800,000 viewers in English.

While 2.1 million is an impressive number for a country that isn’t as fanatical about soccer as the rest of the world, it’s not even the highest-rated non-World Cup soccer match on U.S. television in the past year: 4.7 million people watched the final of a Mexican soccer tournament, Liga MX Clausura, on May 18, 2014. That game’s average audience was 2.5 million — in Spanish on UniMas.

By contrast, the 2010 and 2014 World Cup finals gathered 24.3 million and 26.5 million U.S. viewers, respectively — with 9.2 million viewing the 2014 final in Spanish on Univision.

Let’s use that to do some arithmetic about El Clasico’s audience globally. We know that El Clasico viewership in the U.S. (2.1 million) is less than one-tenth that of the World Cup’s viewership in the U.S. (24.3 million in 2010). If the world had similar proportional viewership, it would suggest an average global viewership of El Clasico more in the 50 million range.

If we looked only at relative viewership in Spanish (the subset of Americans most fanatical about soccer), however, it would suggest an average viewership of about 75 million worldwide. If we wanted to be arbitrarily charitable, we could assume that worldwide interest in El Clasico might dovetail with Spanish-language American interest in the Liga MX final — which would suggest an average worldwide viewership of about 144 million. Although this would be higher than the Super Bowl’s average viewership in the U.S., it would be within the range of estimates for the Super Bowl’s total average viewership worldwide (a number that has its own difficulties being pinned down).

El Clasico in the Messi/Ronaldo era is an amazing spectacle and deserves much of its Super Bowl-level of hype. But it doesn’t need to be an urban legend to be legendary. Sunday’s game featured a wildly bended assist from Messi on a free kick, a Ronaldo equalizer from a gorgeous behind-the-back pass, and a thrilling decider by star striker and sometimes-cannibal Luis Suarez. I enjoyed watching it, no matter how many people were doing the same.