Unreliable sources:
1. https://www.statista.com/statistics/944559/worldwide-macos-version-market-share/ states
Note that the source has indicated the fact that Apple has been reporting Big Sur 11 as Catalina 10.15, making its reported market share incorrectly high.
2. https://gs.statcounter.com/macos-version-market-share/desktop/worldwide
Apple are incorrectly reporting Big Sur 11 as Catalin 10.15. You can read more about it [here](https://bugs.webkit.org/show_bug.cgi?id=216593).
Seems like no one really knows what the actual numbers are?