Our friends over at Developer Economics recently did a really great write-up on tracking the success of your app. Although we tend to think of success in terms of revenue, an app’s bottom line is not the only measure of popularity, nor is it necessarily the most useful performance indicator.

In a more specific sense, revenue doesn’t necessarily give you an exact idea of where your users are coming from, nor can it give you an idea of how the app is going to perform over time. When it comes to assessing the app’s present and long-term performance, it’s often much more useful to look at metrics like cost-per-installation (CPI), engagement, and retention.

CPI means exactly what it sounds like – the cost you paid to acquire a user and get them to download the app. Although CPI is typically calculated based on the cost of an advertising campaign, it might also be useful to include the cost of porting the game to its relevant platform app store.

Engagement is measuring metrics such as how often a user opens your app, and how long they use it during a typical session. It’s essential to remember that many apps will different definitions of what

an “ideal” session length will be. Even further, some apps will have low session lengths but will consider themselves successful because they have a high “Time in App” (TIA) metric. For example, you may only use your phone’s calculator for seconds at a time – but if aggregated the total amount of time spent in the calculator app, you would see a very high TIA, indicating that the app was used fairly often.

Retention is a measurement of how often new users keep on using your app. Again, the definition of “successful” retention will vary from app to app – but I’m sure most of us could agree that the longer that people use our apps, the better.

Check out the full entry on the Developer Economics website.