There's a BioShock 2 interview on WorthPlaying talking with Allen Goode of Digital Extremes about their contribution to BioShock 2 multiplayer. They cover various aspects of multiplayer play, along the way explaining the ranking system they've devised: "We rate skill, and when I say 'skill,' I don't necessarily mean the rank you see as a player. As you progress and gain ADAM, you'll gain rank and you'll see a little number beside your name. That number is more representative of your experience level or how much you've played over time but not necessarily your skill. Behind the scenes, we have another number that is what your actual skill ranking would be as a player. If I'm a new player, I'd obviously be ranked zero. It would have a hard time determining who to put me up against, aside from other zeroes. Preferably, the system will try to match you with players who have a similar skill level, rather than an experience level."