Is this a joke on your part??? It says this: "Adjusted Total Quarterback Rating, which values the quarterback on all play types on a 0-100 scale adjusted for the strength of opposing defenses faced." And you think (your words) "they've defined all the ingredients of QBR". LOLOL. Have you NEVER read a marketing label before? When a company says "We did X" that does NOT imply they didn't do Y. lol. Seriously, man don't be so naive. Regardless, ESPN themselves tell you they use air yards and QB pressures as well as MUCH more: https://www.espn.com/blog/statsinfo...-calculated-we-explain-our-quarterback-rating It's that "division of credit" where the subjective part comes in. There's no real statistical way to do that in practice. Theoretically you can compare variances in some stat (e.g., win%) when you replace one player vs. another and show that variance in that stat was X times greater in one case than the other, thus estimating the relative contribution of both positions. But in practice you can't really get that kind of data. So anyone going around saying they have some way of "dividing credit" amongst players is just inserting subjective assumptions. Same is true for DVOA. In any case, 10,000+ lines of code makes sense when you try to take into account anything and everything you think might be important but don't know how best to incorporate all those variables. And precisely because you made all kinds of ad hoc assumptions you keep it secret instead of showing the world how brilliant you are lol. ESPN QBR is a joke. If it's that similar to EPA they should just use EPA and be done with it, but no they'd rather act like they have something special when they don't.