IBM does studies, though they are to be taken with a grain of salt. http://www.cio.com/article/3001871/macbook/switch-to-macs-fr... Thing is they're one of the few companies that are proponents of both Mac and Linux (plus their own UNIX variant) as well as Windows.

It really depends on the company and the nature of work people are doing. Some software is a mess on anything but Windows. Some software is actually better on Linux.