Halo BPR

I think this stat has been around for a few months, but the new Halo Waypoint makes it more obvious.  Battle Proficiency Rating (BPR) is a number between 1 and 100 representing a player’s overall skill in Halo: Reach’s Multiplayer mode. This rating tracks your Kills, Wins, Assists, Deaths, and Betrayals across all matches played. You must play at least 10 Invasion, Arena or Competitive games to calculate.   i.e., it's an overall rating of "how good you are."  Interesting to peruse the clan numbers.  :)