I truly applaud the amazing footprint Flurry has achieved in the mobile app ecosystem. It's not easy for a new company to carve out its space in a growing and crowded marketplace.

Flurry has been at the forefront of teaching developers, whether indie or not, the importance of understanding user behaviour and analytics.

On top of that, it has become the close to "de-facto" analytics toolkit that every up and coming developer uses in their releases. This is an amazing achievement given the especially competitive nature of the mobile sector.

Flurry packs in a ton of useful features, and when you put its analytics to appropriate use, you can extract some truly valuable information.

However, there's one rather crucial area where both Flurry and its credibility as an analytics platform stumbles. Let me explain.

Devil is in the detail

Retention is the number one key metric upon which all other elements of a well functioning freemium economy are built. Retention is the foundation for a freemium economy.

Don't believe me? Check out Eric Seufert's excellent Minimum Viable Metrics for some background information.

As Eric explains, rentention enables the other three pillars of a freemium economy - engagement, virality and monetisation - to work, at least on a theoretical level. Consequently, without appropriate retention metrics, the other three pillars fall apart.

Wilhelm Taht

Retention is the #1 metric that developers and publishers study when a freemium game or app is launched. It's studied in detail when "soft launching" a game in a single country (just as Supercell, for example, is doing at this very moment doing in Canada with Boom Beach and Glu with FrontLine Commando 2).

Retention is studied in detail by management of developers and publishers of freemium games. It is studied in detail by venture capitalists. It is studied in detail by product managers. It is an important metric for a freemium product.

Simply put, the retention metric the industry is interested in is defined as the "percentage of users that came back to your game on the Nth day after first using the app", better known as 'Day N Retention'.

When looking at Retention figures, the industry usually looks specifically for day 1, day 7, and day 30 figures as the benchmark for calculating a user's lifetime. And eventually the Lifetime Value of the user, when adding monetisation to the equation.

In the world of freemium mobile and tablet games, the minimum retention thresholds that the industry is looking for are usually defined as:

• Day 1: minimum 30 percent (preferably 40 percent) of users who downloaded the game on "Day 0" return to the game
• Day 7: minimum 15 percent (preferably 20 percent) of users who downloaded the game on "Day 0" return to the game
• Day 30: minimum 8 percent (preferably 10 percent) of users who downloaded the game on "Day 0" return to the game

Unknowingly to majority of the industry, Flurry does not show this type of metric as retention. Instead something Flurry shows something it labels Rolling Retention.

Flurry's definition for Rolling Retention is the share of users that came back to your app on the Nth day after first using the app, or any day after the Nth day.

At first glance, the difference might not seem apparent or crucial, but when you dig a little deeper it becomes clear that it is.

Simply put, 'rolling retention' has absolutely nothing to do with our previous definition of retention. In fact, what the metric shows is the opposite of churn (100 percent – Your 'Rolling Retention' stat = your churn).

The real issue

Churn is defined as how many users have quit your game "forever".

Usually – though not always - developers and publishers quote Flurry's Rolling Retention metric as 'Day N Retention', which it isn't. Now, for a publisher or a developer of mobile games, the metric becomes especially problematic for a few reasons:

• The metric will always be higher for a game (or an app for that matter) that has been on the market for a long time.
• The longer an app is installed on a user's device, the more likely a user opens it again. When the user does open it again, he or she is put into the pool of retained users across the full time period - I've seen slightly older titles that show a 90 percent day 30 retention, using Flurry's 'rolling retention'. If only
• The metric gives very limited information on the true nature of the game or apps quality or user base
• Indie developers are unaware of what the "rolling retention" metric means, and will make uninformed decisions on it. Or alternatively, waste time in development cycles when adding other analytics toolkits, as they finally understand that Flurry does not show the metric they are looking for
• Venture Capitalists and Product Fund Managers are unaware of what the metric means, and might make uninformed investment decisions based on it. (VC's - please do take note of this!)
• Publishers are time after time again shown excellent retention metrics for developers' apps and games, which are completely useless for informed decision making

Long story short, the "rolling retention" metric Flurry pushes is not something that gives any valuable information to its observer.

In fact, the only thing the metric is good for is to display to uninformed venture capitalists when fishing for an investment, along with other non valuable metrics such as "total amount of downloads", for example.

Having endured this same conversation with countless developers explaining what the problem with Flurry's take on retention is – andknowing that we at Playground Publishing aren't the only ones to take issue with it – I can only hope Flurry quickly shifts is approach to retention for the good of all its users.

UPDATE: Flurry has publicly responded promising to provide 'static retention' (or 'Day N retention') within the next few weeks.

Wilhelm Taht is COO at Playground Publishing having worked within the fields of online, mobile and social media for the last decade. He also serves as an adviser to several startups in the fields of games, media and music. You can follow Wilheim on Twitter here.