In order for that study to be of use, seems to me you'd have to figure out a way to account for the times a strong arm kept an outfielder from having to make a throw. On a shallow sac fly, I suspect a runner on third is a lot more likely to run on Manny than Ichiro. You're absolutely right... however, you could account for that by simply changing the number of throws to number of opportunities. Runner on first, see how many times a ball was hit to right vs. the number of times it was hit to left. I might be way off base, but I'm willling to bet that my theory is pretty accurate. That assumes all hits to the OF are the same. A harder-hit-than-normal single isn't as likely to advance a runner as a weaker one. And the odds are higher that a blooper with less than 2 outs will keep things station to station, regardless of where in the OF it was hit.