AppBrain published statistics on library usage on Android. This list of libraries is very interesting and to me quite surprising.

These stats are presented on three tabs: "Ad networks", "Social SDKs" and "Development tools". Here I care about development tools only.

For example the two most-used libraries are those of the leading analytics providers,

Google and Flurry. No surprises here. But what is surprising, is that together they are used by less than 14 per cent of all apps. Why is this number so low? I would have guessed that most apps, that need an internet permission anyway, would also use one of these packages. After all, we are interested in usage patterns, aren't we? How else should independent developers improve their app, since they do not have the means to conduct extensive and costly usability studies?

Even though only about 13.5 % of all apps available in the store use these packages, 36 % of all installed apps have this package on board. If you drill down into the data (by clicking on the library) you see, that more successful apps use analytics more often than others. Together both libraries are used in 60 % of the top apps. Quite a difference. Still I wonder why the developers of less successful apps do not care about these data. Maybe because for top-developers much more money is at stake?

The third library in the list is the Android Support Library. Also no surprise here. But while 6 per cent use this library only a shockingly low 0.96 % also use ActionBarSherlock. Huh? Why is that? This is IMHO depressing - and, no, I have no affiliation with +Jake Wharton at all. But I think the actionbar pattern is very useful and should be part of most apps. And Android's design guidelines think so as well:

The action bar is arguably the most important structural element of an Android app.

ActionBarSherlock is such a a great library to support this pattern on older versions of Android as well - so why not use it?

Another surprise is the near absence of gaming libraries. I could only spot libGDX, AndEngine and Unity3D which are used by roughly 1 per cent of all available apps each. With 6 % usage among installed apps it's a bit better. But, come on! About 25 per cent of all installed apps are games. Why then are there not more gaming libraries in use? Do game developers love to write their own engines? Well probably. But nearly all of them?

The picture is quite different for the tab "Ad networks". Admob is used by 33.49 % of all available apps and 46.99 % of all installed apps. Whow! That's finally a number I am not surprised about. Well, perhaps that one network is that dominant. But that ad networks are used a lot, that's no surprise. We see ads every day - and most of use make use of these networks as well.

But still: To me some of these stats simply make no sense. Maybe some of you can explain these numbers? Or are these numbers what you would have expected anyway?