Much attention has been focused on the growth of Android Market of late, as developers look for a second stable marketplace to sell their wares outside of the App Store.

But while Android Market is adding apps at a faster rate than its great rival, it's also losing more of them too, leading advisory firm asymco to brand developers on Google's OS as "less persistent" than their iOS brethren.

War of app attrition

Asymco founder Horace Dediu makes reference to 'app attrition' – i.e. the difference between the number of apps currently available on a platform and the cumulative number of apps that have been approved for sale during the marketplace's history.

In essence, the difference between the two figures represents the number of apps that have been removed from sale – either by the publisher, or the platform holder – at some point post launch.

"What makes this interesting is the contrast between attrition rates on Android's Market and those on Apple's App Store," Dediu states.

"About 80,000 (or 16 percent) of Apple's catalog has been removed while nearly a third of Android apps have disappeared from the catalog."

Marketplace mystery

As such, while Android Market is gaining 30,000 new apps a month to the App Store's average of 20,000, a greater share of its existing library is, for one reason or another, being removed from sale than on its counterpart.

"The challenge for an observer is to reconcile the growth in Android submissions with the apparently far higher attrition rate," Dediu concludes.

"In other words, Android developers and producers seem to be more prolific but less persistent.  With few if any constraints on submission it’s understandable that there will be more apps thrown into the catalog.

"But why would they be so rapidly removed remains a mystery. Maybe economics, maybe policing, maybe something else altogether explains this."

[source: asymco]