Just took a look at MSFT. I was surprised to see that the stock has been climbing basically linearly for a solid 5 years now. I wanted to revisit the CEO/stock price graph now that we've seen a bit of Nadella's performance:

http://i.imgur.com/lr9j2KS.png

I was expect to see a nice perfect correlation of Ballmer = flat stock price, but it actually looks like the upturn began during his tenure. Speaks well for him, although overall it's not a pretty picture of his tenure.