It isn't really, tho. It's established by the compensation committee that is convened by the board and comprises of board members.
Starboard bitched about the compensation committee since it only had 2 members on it, and they were favorable to Mayer (giving her credit for what is effectively a rise in Alibaba).
Starboard got 3 of it's own board members onto that committee now, so the fun times are over.
The conflict of interest in the process has always been that you have your own board members, some of whom you bought into the board, deciding compensation. A lot of these directors are themselves the subject of compensation committees at other public companies - so there is a quid pro quo amongst those who serve on each others boards.
It takes an outside activist investor to break up these friendly and circular compensation cliques.
I like Mayer, but it is really difficult to justify these compensation packages when the core business she is running is performing so poorly. I don't think many people would have any problem with her earnings hundreds of millions of dollars - but only as a portion of gains made by rescuing Yahoo's decline.
But the bottom line problem with CEO pay is that you get a huge pay packet just for getting out of bed, no matter how badly you do; pay is completely decoupled from performance.
When Leo Apotheker was at HP for just under a year he received $13m in comp, severance of $7.2m, shares worth $3.56m, and a performance bonus of $2.4m - all while losing $30bn in value.
Developers like to speculate about 10X programmers. But ahere's no industry acknowledgement at all that the 0.001X CEO or manager is a real phenomenon. Anyone working at that level seems to be completely protected from business consequences.