I worked for a major Novell distributor in the early nineties. At the time, the SUGGESTION from Microsoft for help desk staffing was 1 tech per 50 - 100 users, depending on the level of automation that could be done (this was Win 3.1, including server). Novell recommended 1 CNA and 1 CNE per 30 - 50 servers, but that varied according to the applications running on the NW servers.
The reason Novell bought USL (Unix Systems Labs) from AT&T was that 1 Unix admin could support as many as 50 - 75 servers, again depending on application type. UnixWare could run Oracle DB, and that meant there was a requirement for support admins for those "specialized" applications.
In 1994, Novell spun the Caldera group (which started as a lightweight desktop replacement for Windows) off from Novell. At the time, I was still closely connected to Novell's Unix products group mostly through Kent Prows, who had fathered UnixWare through development. I was told at the time that Novell saw the Caldera project's success, and immediately ceased further development on desktop UnixWare, because "this Linux thing can do everything UnixWare can." That was from one of my other contacts at Novell.
The reason for the digression was that Microsoft had popularized Windows through the CIO and IT departments as "minimum wage administration" (verbatim from an MS distribution rep) and Novell had the burden of showing that UnixWare had all of the advantages of Windows in ease of use, etc. However, they had to get over the fact that Corporate Types have an intrinsic desire to build an empire, and that meant plenty of foot soldiers, and hence the bigger Table of Organization meant more pay. They (CxO's) like that Windows takes more staff; more staff, more pay.
BTW, at the time, Macs took 1 admin per 200 - 300 workstations, because of the better quality of software, and more necessity of reliable OS; because Apple had to support all of the Macs out there in home user land. I don't think that has changed significantly.
So there you have it; because I sold Unix systems to all levels of the Federal Government (the CIA loved SPARC stations; but they ground them up when they were obsolete), I had to be pretty aware of these numbers.
You can probably find out today's staffing levels from the respective OS manufacturers, search their sites for "enterprise staffing levels".
And good luck with your quest.
Dave Lawson