There have been some good questions about the Team Health Reports and the underlying system, especially over at Dodger Thoughts. First, I’ll point everyone to this article, which explains much of the underlying system.
The bands — what you see as red, yellow, and green — always get a lot of discussion. Why do I choose to use bands and what do they mean? Yes, the system has an underlying “number,” a percentage that is both more specific and more error-prone. It’s one thing to say “Zack Greinke is a 12″ or “Darren Dreifort is a 101″ but I don’t know that it means much more than the bands. Is 12 that much better than 13? 20? By banding the ratings, I can give you much more meaning and it’s much easier to read.
The bands were initially set at 33 and 50*, but have moved off that slightly based on the changes in experience for the underlying actuarial table. They’re designed to be measuring risk, not cutting the population in thirds, though I can understand why some think that.
As I’ve said, the ratings are just a broad measure. Sometimes I agree, sometimes I disagree (with my own system!), and sometimes it confuses me. All that will be detailed in the team writeups, which is why I always say pay more attention to them and why we work hard to get them out to you as soon as possible.
(* meaning that green was 0-32, yellow was 33-49, red was 50-100)