Cast an eye back to April, when Google’s Ice Cream Sandwich update for Android had been available for almost six months, yet it had only found its way onto less than three per cent of Android devices.

Looking at the same statistics today, ICS has moved up to an install base of almost 21 per cent. That’s an increase of 18 per cent in five months.

As device vendors and carriers finally get around to releasing ICS updates to devices that had previously been running Gingerbread, this percentage will continue to increase; also due to the extra 20 million ICS-running devices that have been sold in the last three months.

The latest update to Android, Jelly Bean, comes in at 1.2 per cent, two months after its release.

Android’s venerable Gingerbread release decreased by 6 per cent over the intervening five months, Froyo fell from 9 to 14 per cent of the Android install base, the other non-4.x releases of Android (Cupcake, Donut, Eclair and Honeycomb) all saw decreases, as well.

With 1 in 5 Android devices using a 4.x release, developers can start considering the new features delivered by ICS more seriously.