Previously, this was part of our replacement level calculation, but it has now been moved into Runs Above Avg."Park Factor customized for parks the pitcher threw in From 1918 on, we have full gamelogs, so we can say exactly how many innings a pitcher threw in each park.
Note the one-game park factor is the team PPF/100 minus 1 times two plus one, since the factors on team pages are for home and road games combined." - RA9)/9, then centered so the league average is always zero.
It is the number of runs this player is better than an average player.