If you subtract MS employees and those who do significant business with MS or have many MS stocks, the number will shrink further.
The users wouldn't mind going to a Mac, but the problem is that the software isn't there. Sure, there's some business software available for Macs, but it's generally small business software, and limited to general purpose. Most businesses now run on Wintel software.
Like Linux, maybe if more software gets ported over to the Mac, it will be ready to do battle with Micro$oft.
Mark