Just because Google keeps periodically releasing new versions of its Android mobile operating system, as it did with Android 6.0 Marshmallow recently, does not mean that device vendors and users are keeping pace.
In fact, the vast majority of Android devices in use globally are on versions of the operating system that are at least two years old, or older.
Google's most recent dashboard on the relative number of devices running a given version of Android shows that nearly 40 percent of installed devices are on KitKat, which the company released more than two years ago.
Another 30 percent or so of the installed devices have different versions of Jelly Bean running on them, including the first version dating back to July 2012.
Some 7.5 percent are based on Android Gingerbread and Ice Cream Sandwich—versions of the operating system from 2010 and 2011.
Meanwhile, only 23.5 percent of Android devices have Lollipop (Marshmallow's immediate predecessor) installed, just one year after the operating system came out.
Since Marshmallow was only just released, no numbers are available for it as yet. But Google is currently shipping the operating system preinstalled on its recently introduced Nexus 6P and Nexus 5X smartphones. The OS is also available as an over-the-air update on other Nexus models.
Google's Android adoption numbers show that the operating system versions on a majority of Android devices are at least two generations behind the latest release. In contrast, iOS 9, Apple's latest version of its mobile operating system is already installed on more than 60 percent of iOS devices, barely one month after launch.
Android's uptake numbers are symptomatic of an OS that is designed to support multiple architectures rather than a single architecture such as Apple's iOS, said Steve Brasen, managing research director at analyst firm Enterprise Management Associates.
Typically, Android updates can occur only if three conditions are met, Brasen explained. The device CPU, memory and other hardware components must be sufficient for running a new OS. The device manufacturers have to update device drivers and applications for the new operating systems and end users need to enable automatic OS updates on their platforms to receive the new releases, Brasen said.
"Given the fact that the convergence of these three conditions is rare for legacy devices, most OS adoption occurs through device attrition, rather than system updates," he said.
"Since the lifecycle of a mobile device is roughly three years, it takes about that long for a new OS to gain dominance," he said. So it is no surprise that KitKat, released in 2013, is the current leader. Lollipop on the other hand is just one year old. So don't expect to see broad adoption of the operating system till at least 2016, as new devices are adopted to replace older models, Brasen said.
Google has received some flak for not doing enough to maintain or police the updating of older Android versions, said Charles King, principal analyst at Pund-IT. "But I believe that doing so would likely significantly impact Android uptake without delivering significant benefits," he said.
One of the reasons Android adoption is all over the map is because vendors and manufacturers need access to old versions of the operating system that are capable of running on inexpensive commodity hardware, King said. "That's a critical factor in cost-conscious markets, particularly in emerging economies, and one reason that Android does so well among those users."
Uniformly updated versions of Android would probably be beneficial for users, he said. "But markets and their customers, especially when considered globally, are anything but uniform. Google seems to understand that point."