from Amazon
Wednesday, February 18, 2009
Individualized Park Impact numbers
We’re not there, but this work from Brian is one step toward there. If I’m reading the first line correctly: for parks that severely depress HR rates (70% decrease for all players), the power hitters lose only 50% of their HR rate, while the weaker hitters lose more. At the other end, for parks that add alot of HR, the power hitters gain very little, proportionately-speaking, compared to the rest.
This is exactly what we should have expected. I also think it would be just as instructive to see the differential changes. Let’s take the last line, where the park factor adds 90% over the average player’s mean of .040 HR per contacted ball. That means, the average gain is +.036 HR per ball. The power hitters are at, say .085 HR overall, and in this park they gain 29%, or a gain of +.025. On the other end, those with a rate of .015 HR per ball hit 2.9 times as many HR or .044, or a gain of +.029.
See where I’m going here? I would not be surprised that if we go through Brian’s entire chart, and instead of showing it as ratios we should it as differentials, and that we will not find much difference, differential-wise, among all the classes of players.