Just two and a half years after the launch of the iTunes App store it has today reached the milestone of 10 billion downloads. This means that more than 60 apps have been downloaded for every iOS device sold.

Apple hit the 10 billion mark for downloads of apps from its iTunes App Store around 10:30 am GMT on 22 January.

In anticipation of this momentous event, data comparing the downloads for the iTunes music store and the iTunes app store have been analysed by Horace Dediu of asymco, who points out that the 10-billion download threshold , has been reached for apps in less than half the time it took for song downloads, as shown in this  chart.

What is even more heartening for app developers is that 10  billion downloads divided by the number of devices sold shows that over 60 apps have been downloaded for every iOS device sold.

The chart shows that in late 2008 there were 10 apps downloaded for every iPhone/iPod touch and that 2 years later the rate was more than five times higher.

According to Dediu another way to look at the data is the daily download rate where he has fitted linear trendlines to show a clear trend and add data from Nokia's Ovi for comparison:   

Dediu's own comment on this is:

The amazing story of this chart is not that apps are running at above 30 million download per day, but that the figure is growing. Growth like this is hard to get one's mind around. Not only are downloads increasing, but the rate of increase is increasing.

The fact that the rate at which apps are being downloaded is still increasing has to be good news the app developer. It suggests that there is hope that the app using phenomenon is not just a short lived fad. Users have embraced the idea of small focused applications that are easy to download - and perhaps even easy to dispose of after users have grown bored with them.