The only fair way to promote in largish organizations is to promote those obvioulsy outperforming anyone else (rare), exclude those obviously not performing, an

The only fair way to promote in largish organizations is to promote those obvioulsy outperforming anyone else (rare), exclude those obviously not performing, and then put everyone else into a lottery. Almost no matter what you do, people will get promoted until they are no longer competent, so it's best not to put too much effort into deciding. In fact, if you're worried about lawsuits, just put everyone into the lottery and promote that way.