About 20 percent of Instagram users connect to Facebook through the mobile photo sharing app each month, according to an analysis using our AppData tracking service. This is up from 15 percent last year, and numbers related to Instagram’s Android release last week suggest the proportion could be even higher.

Facebook announced Monday it would acquire Instagram for $1 billion, allowing the app and brand to live on. Facebook CEO Mark Zuckerberg says Instagram will continue to support cross-posting to other social networks and allow follower/following relationships without forcing users to connect on Facebook. That will be important, as a relatively small percentage of Instagram users seem interested in linking their accounts. However, as the two services develop closer ties, Instagram could include more compelling reasons for cross-over; for example, tagging Facebook friends and Facebook check-ins.

Nine months after its public launch, Instagram announced it had 5 million users. At that time, less than 15 percent of these users were using the photo sharing app to connect with Facebook each month, according to AppData. By this we mean users posted Instagram photos to Facebook directly from the app or used Instagram’s “find friends” feature. Since then, the percentage of users connecting with Facebook and using the app each month has grown to slightly more than 20 percent. Instagram’s Facebook app has 7.3 million monthly active users, though Facebook hasn’t updated its user numbers in several days, as seen in the graph below.

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