Park Factors
Market-specific park factors for all 30 MLB ballparks — switch between strikeouts, hits, home runs, and total runs.
How Park Factors Are Computed
What it measures: How much a park amplifies or suppresses pitcher strikeouts vs. the league average (1.00 = neutral). A factor of 1.05 means pitchers at that park record ~5% more Ks than average for the same pitcher quality.
Method: We aggregate pitcher strikeouts and batters-faced from BDL regular-season games at each venue (2024–2026), compute league-average K rate, then derive a raw park K rate ratio. Small samples are regressed toward a FanGraphs-calibrated prior with ~2,000 PA of weight. Dome/retractable-roof parks show more stable factors since weather doesn't contribute.
Model usage: The park K factor is applied as a λ multiplier in the Poisson strikeout model alongside weather, age curve, whiff%, opponent K%, home field, and umpire zone tendency.
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