Monthly average user. Uptime for Win 11. Uptime not counting screensaver. Uptime for non-enterprise consumer. If you were a Win 11 enterprise user, then Uptime for enterprise users. Unique hardware indicators - number of distinct PCs in Win 11 ecosystem, separated from new activations. And I'm sure a few others that I haven't thought of.
Declining stats on these measures indicate a problem somewhere in the Win 11 ecosystem. Combine with competitor indicators like sales, and other Win ecosystem OSes.
A single person switching probably doesn't do much to move the indicators. But as a collective?