Not "finding". I had to calculate all that stuff myself. And yes, I was very bored, and yes, I do this kind of thing for fun. Yes, I am a geek.
After Warner's retirement, I was arguing with some friends about his fumbling and how bad it was and what it meant, and we didn't get anywhere because we didn't have any context for the discussion. How bad was he at holding onto the football? How bad was his hand? How much fumbling is a lot? How much is very little?
So I started running numbers. If you look at fumbles per game, it makes guys like Marino and Manning, who played behind excellent offensive lines and had quick releases, look fantastic. But that doesn't help to put Warner in context. If you use pass attempts, the results tend to be very unfair to running QBs, the Cunninghams and Vicks, and Stewarts, because every rush is a chance to fumble, but not an attempt, which skews the numbers.
In fact, without subdividing all fumbles into categories, (botched snaps, botched handoffs, sack fumbles, rush fumbles, etc.) and calculating each seperately, nothing's gonna be perfect. What I settled on was dividing the QB's fumbles by the number of times they got hit with the ball in their hands. That is, sacks+rushes+receptions+fumble recoveries. All of those are chances to fumble. The last two categories are, in most cases, non-factors, but I include them for the sake of completeness.
The weakness here is that a goodly percentage of fumbles occur on snaps or handoffs. It's also a bit unfair to pocket passers, who don't get to increase their denominator by running the ball. So you have to keep in mind what kind of QB you're talking about, and it isn't perfect. But what stat is? The idea is just to give you an idea of what QBs have the hardest time holding onto the football, and looking at it on a per-hit basis seems like the best way to do that to me.
Whew. Anyway, the results were pretty stark. Warner's career numbers were horrible, far worse than the next worst quarterback. And the difference pre and post hand injuries was stark too, taking him from essentially average, to just ungodly bad. And they didn't really show improvement after the gloves, which surprised me at the time.