According to the latest statistics released by Google, only 36.2% of Android phones are running the most current version of the operating system, and 23% are running versions that are over a year old. Here's the current rundown of how many Android phones are using each version of the platform:
< Android 1.5 - 0.1%
Android 1.5 - 7.9%
Android 1.6 - 15.0%
Android 2.1 - 40.8%
Android 2.2 - 36.2%
So the most common version of Android that users are currently running is 2.1. This was the version of Android that almost all phones had during this year, bringing adoption rate high. However, a lot of people who bought an Android phone in the last several months have not yet received their upgrade to version 2.2.
Samsung's Galaxy S phones, and other models from HTC, LG, and Samsung have not been upgraded. The entire Droid family has gotten updated to the latest Android platform, but that certainly only represents a small portion of people who've bought an Android phone.
Some of these phones are pending an upgrade, but some simply will never receive it. The same goes for phones below Android 2.1, which represents about a quarter of all Android phone owners.
These latest numbers come just as people start to focus their attention on Android 2.3, which will actually be coming out before too long. The Nexus Two, which will be officially unveiled next Monday, is expected to be the first phone to run the next generation of Android.