Park factors in this piece are a three-year average from 2016-2018, indexed (100 = average). For example, left-handed home runs at Guaranteed Rate Field (home of the White Sox) have a three-year index of 117, which means there have been 17% more homers hit by lefties from all teams during that span in that park compared to a completely neutral environment. Left-handed hitters have a significant advantage when hitting at Guaranteed Rate Field.
AT&T Park (home of the Giants), has a three-year run index of 95, which means that games played at AT&T park have had 5% fewer runs scored overall than a completely neutral environment. Overall offensive production is reduced by a significant amount for games played in San Francisco, making it a safer environment than most for pitchers.
