Definition
WordPress plugin download change by tag is the change in combined downloads among plugins that share a tag on WordPress.org. It adds up the downloads of every plugin carrying the tag, and compares the month with the one before. The tag is chosen by each plugin's own author, not by Rivale.
Population and window
Rivale measures this across the top 12,500 plugins, limited to tags used by at least 100 of them. Issue 1 compared four full weeks. Later issues compare full calendar months, per day, because months differ in length. Both date ranges are stated beside the figure in every issue.
How it is computed
The sum of downloads across the plugins that use the tag. “Gained the most” and “lost the most” are ranked by downloads, not by percentage. A tag is included when at least 100 of the top 12,500 plugins use it. The rule is the same in every issue. Most tags on WordPress.org are used by fewer than five plugins. Plugin authors choose their own tags, and a plugin with several tags is counted in each of them.
How to read it
One large plugin can move a whole tag's total. A plugin with several tags is counted in each, so tag totals must not be added together. Read it beside download change for individual plugins carrying the tag. Read it beside top-3 install share for the same tag to connect download movement with install concentration.
What it is not
It is not the typical plugin's change: a tag can gain overall while most of its plugins lose. Tags used by fewer than 100 of the top 12,500 plugins are left out entirely. Most tags on WordPress.org never appear in this measure. It is also not a count of how many plugins carry the tag.