When looking at pitching performance histories and you look at the pitchers best, worst, and average seasons...to the right of all this are various plus and minus numbers under the heading Ballpark. Does anyone know what this means? It shows singles, doubles, triples, HRs and plus and minus numbers kind of like the ratings you see for the ballparks. Is this the instances of how the pitcher gives up each hit? Or is it perhaps the ballpark he performs best in?

Those are the park factors for the home ballpark of that particular season.

Ahhh thanks....that makes complete sense.