The 5 different types of Apple users

One of the big questions facing any Apple shareholder is whether Apple's userbase will continue to grow and how much money per user Apple can expect to earn.

Steven Milunovich, a UBS Securities analyst, publishes regular investor notes looking at exactly how big Apple's installed base is and what its revenue per user is.

His latest analysis suggests Apple could add 92 million iPhone users in 2017 and 82 million in 2018.

He concludes that although Apple's installed user base growth is poised to "slow due to size and increased competition," after that, the amount of money Apple makes per user should increase and stabilize at $340 per year - even if Apple doesn't release a new product.

Milunovich derives his per-user statistic by breaking down Apple users into five classes based on UBS surveys and Apple's corporate reports:

Notably, his analysis suggests that users switching from Android may comprise 15% of the Apple userbase over the next two years. This is because Apple generally has a higher retention rate than Android, according to a UBS study.

Here is the UBS unweighted estimate of smartphone retention rates by brand:

After weighting, Milunovich assumed that 85% of iPhone users would stay with Apple and 75% of Android users would stick with an Android manufacturer for his estimates.

Ultimately, UBS concludes, "we see two more years of double-digit installed base growth driven by our upgrade model and new users." UBS rates Apple stock as a "buy" with a price target of $127.