A few months ago, we passed along a report that Facebook was urging its employees to swap out their iPhones for Android devices. It knows Google’s mobile OS has continued to be an afterthought to iOS, and it’s looking to change that.

Well according to some newly-released data, that’s probably a smart move. Enders analyst Benedict Evans has just published Facebook’s mobile app user stats, and, as of November last year, Android users vastly outnumber those on iOS…

From Benedict Evan’s blog (via TechCrunch):

“Until late last year, Facebook disclosed monthly active users (MAUs, hereafter ‘users’ for simplicity) for its smartphone apps, on a rolling daily basis. I was always slightly nervous of publishing it, since you had to know how to get it and I suspected it might disappear if anyone pointed it out. Now, like fairy gold, the data has disappeared, so I can share it. “

As of September 2011, Facebook for Android had 66 million users and Facebook for iPhone had 91 million. But just 11 months later, in November 2012, Android grew to a staggering 192.8 million, while iPhone only accounted for 147.2 million.

facebook mau data

Interestingly enough, though, the iPhone has a much better penetration rate. Facebook’s native app is actively used by 73.6% of the estimated 200 million iPhone install base, compared to only 35% of the estimated 550 million Android install base.

Other notable figures include 48 million active iPad users, and out of the nearly 200 million total iOS users, only 53.8 million have turned on iOS 6’s Facebook integration. I also found RIM’s 60.2 million, and Windows Phone’s ‘few’ million users interesting.

Of course, these numbers are a few months old, and I’m sure there are other anomalies here. But it’s no secret that many developers, like Facebook, continue to have an iOS-first mentality. And as fast as Android is growing, that may not be the case much longer.