Earlier quoted context omitted.
Microsoft has been doing stack ranking long before 2006. I left in 2005'and attended stack rank meetings, where managers indirectly decide your review score before you even get the form from HR. it goes back to at least the late 90s, IIRC.
Were those in the bottom rank shown the door in due course?
It was based on a model proposed by Ballmer's hero Jack Welch. What Ballmer forgot is that Welch himself said the "trim the bottom 10%" model didn't work once a company got larger than a certain size.