Relevant OS version usage statistics: <a href="https://data.firefox.com/dashboard/hardware" rel="nofollow">https://data.firefox.com/dashboard/hardware</a>.<p>It appears these operating system versions currently account for about 9%-10% of telemetry-enabled Firefox users, about 14.6-16.3 million users out of the total of 163.2 million telemetry-enabled Firefox users if I'm reading the data correctly.