Park factors

Some parks play small, sit at altitude or get wind that carries. A park factor is the effect a home park has on scoring, with the quality of the teams that played there taken out.

• It compares what happened in plate appearances at a park with what the same hitters and pitchers would be expected to do elsewhere.
• One season at one park is a small sample, so each value also draws on the seasons around it.

• park is in runs per plate appearance. Positive means more scoring than an average park; negative means less.
• pa is the number of plate appearances behind the value. Trust a value more as it grows.
• The values are small. A park at +0.04 adds about three runs to a game with 75 plate appearances.

• park-factors?season=: one row per home park, for every division except NAIA.

• A park is named by its home team.
• It is one number for all scoring. It does not separate home runs from other hits, or left-handed from right-handed hitters.