I stand corrected... Article as of 08.25.16 But I am sure it is higher now.
“Unix and Unix-like operating systems power about 67 percent of all web servers. At least half of those run Linux—and probably the vast majority.”
https://www.wired.com/2016/08/linux-took-web-now-taking-world/
“But I am sure it is higher now.”
Why would you say you are sure if you don’t actually know?
Just search for it. There is all kinds of tracking site out there.