Mobile industry analyst Benedict Evans has published some research into Facebook’s mobile and tablet app users, digging into the company’s claimed 470m app users from September 2012.

It makes for fascinating reading, revealing that 175m people were using Facebook’s Android app in September 2012, up from 66m a year before. The social network’s iPhone app jumped from 91m to 140m in the same time period.

Evans also notes “very interesting strength” for Facebook’s feature-phone app, which doubled to 75m users between September 2011 and September 2012 thanks to its growth in emerging markets.

“Meanwhile the RIM app is growing much more slowly (and had flattened completely by the time the data stopped being reported) and Windows and Nokia are nowhere,” explains Evans, who had been tapping a semi-secret source for the data until late last year.

His conclusion is clear: while Facebook is still figuring out the best user experience for its mobile apps (not to mention the best way to make money from them), mobile is hugely important to its growth.

“Facebook is becoming an mobile app-based service first and foremost. Almost half the base is using smartphone apps and we can be sure it’s more than half the use, especially in developed markets, where 75% of users are on mobile in some form.”