While working on wordpress/gutenberg#4072 today, I was inspired to do some data analysis on the WordPress.org plugin directory.
Based on the initial API request, there are 49,749 total WordPress.org plugins.
Of the entire data set, only 18,002 plugins have 200 or greater active installs. The remaining 31,747 plugins represent an inconsequential number of active installs compared to the total.
The 18,002 plugins represent 182,296,500 total active installs. A WordPress install can have multiple active plugins, so this total isn't unique WordPress installs. Also, we can ignore the remaining ~32k plugins because they would only represent 3,174,700 additional active installs if each plugin had 100 active installs.
Of the total active installs, 168,623,000 (92.5%) are represented by 3,440 plugins with >=5000 active installs. For that matter, 159,720,000 (87.6%) are represented by 2101 plugins with >=10000 active installs.
It'd be interesting to know what percentage of WordPress installs have a plugin not tracked in the WordPress.org plugin directory (e.g. premium or custom).