The color on the map explained:
Blue - current mainstream API version;
Yellow - 6 months;
Orange - 1 year
Crimson - 2 years;
Bright red / white - 3 years;
Bright gray - 4 years;
Gray - 5 years;
Black - 6 years.
Share data with the Android market, Dan Luu created a series of charts to show the growing differentiation of each version of Android.
As for the reasons, Luu speculated there are three possible explanations: (1) Android slowdown; (2) equipment sales slowed; (3) equipment received less and less updates.
Luu writes: "Even using just the data we've got, we can guess how much of the device in use is outdated, and in May 2017 Google announced it had 2 billion active Android devices."
If we look at the latest statistics (the furthest right in the figure above), we can see that nearly half of the devices have failed to keep up with the times. We can infer that there are currently about 1 billion + devices that have not been updated for 2 years.
In view of the Android update mode, it is no exaggeration to say that almost none of these devices can be updated to the latest Android version.