Definition
WordPress plugin update rate is the share of plugins that shipped at least one release during a calendar month. A plugin counts once toward this share whether it released once or several times. The figure measures whether a plugin released at all, not how often. The share is calculated separately by popularity rank.
Population and window
Rivale measures update rate across the top 12,500 plugins, by popularity rank. The window is the report month, shown beside the same figure for the previous month. The two months can be compared side by side within the same issue.
How it is computed
Plugins whose version changed at least once in the month, divided by the plugins ranked at that level. A release that does not change the version string is not counted. A plugin releasing several updates counts once.
How to read it
Update rate moves with how many plugins in a rank changed their version string at least once during the month. It does not move with how many releases each plugin made. Read it beside updates and download change to see release activity beside download change for the same plugins. Read it beside two years without an update for a longer view of release activity. A high update rate at one popularity rank says nothing about the rate at another.
What it is not
Update rate does not count the number of releases a plugin made, only whether it released at all. A release that does not change the version string on the listing is not counted as an update. The figure does not describe the size or content of any release a plugin author made. It is not the same figure as updates and download change. That measure breaks plugins out by release count.
Related measures
Updates and download change, Two years without an update, Download change