Facebook, the undisputed king of social media, has over 1.5 billion monthly active users. It reported 1.49 billion MAUs at the end of June, so let’s just go ahead and say that by now the company has crossed that incredible milestone. That’s over 20% of the world’s population. Just last month, for the first time, Facebook saw one billion users log on in the same day. If you start looking into all the ways this could be inflated, it’s not that impressive. Actually, nevermind, it’s impressive no matter what.

That point is, Facebook is huge. We all know this.

But is Twitter actually bigger?

No, it’s not. But it thinks it is.

Here’s what the company’s CFO Anthony Noto had to say at a recent conference:

“I often get the question from friends [who] are like, ‘You know Facebook has over a billion users,’ and I’m like, ‘Well, we have an audience, depending on how you measure it, that’s pretty comparable.’ But they only have that audience, they only have the 1.4 billion they report, there’s no other number. ​We have other audience numbers that no one talks about and when you add those up it’s a big number, in fact in some scenarios you could argue that it’s bigger.”

Twitter boasts 316 million MAUs, according to its last earnings report. This includes what the company calls “SMS Fast Followers”, or users that access the service entirely via text. Twitter didn’t even count these users toward its MAU totals until Q2. So really, that true MAU number is a bit lower.

Anyway, how can a company with a fifth of the users of Facebook claim to be bigger than Facebook?

This isn’t really a new argument from Twitter. Ousted CEO Dick Costolo made the same one last fall during the company’s earnings call.

“You should think about the size of our total audience as a series of geometrically eccentric circles,” he said, clearly meaning “concentric”.

According to Costolo, and presumably Noto, Twitter’s audience should be seen as not just its logged-in MAUs, but as a combination of those as well as its logged-out users (which total over 500 million, according to Costolo). Not only that, but Twitter’s total audience should include al the people who see tweets embedded in the articles they read online.

Yes, tweets see a lot of eyes. But the main problem is that logged-out users and people who see tweets in random articles don’t see ads. Of Facebook’s 1.5 billion monthly active users, all of them are signed up and seeing ads.

According to Bloomberg, “Noto said he understands that investors don’t focus on Twitter’s wider audience because the company isn’t making money off it. But with new initiatives like Project Lightning, which will make it possible for people not logged into Twitter to tune into events, Twitter could start to make those broader numbers more meaningful.”

Wall Street has been concerned with Twitter’s anemic user growth for a long time. Last month, the company’s stock fell below its IPO price for the first time. I’m not sure this “hidden audience” argument is going to fool anybody.

Image via Andreas Eldh, Flickr Creative Commons