Eras
What a rule change invalidates
Park identity is season-scoped, and a temporary venue is a distinct park era with no inherited priors. The era contract records which comparisons each break forbids.
Open eras →Research preview · 2025 completed season · descriptive
Park run environments
How many runs were scored in each park, against how many the same teams scored on the road. This is a description of what happened in 2025 — not an adjustment, and not yet a prior for anything.
Descriptive only. No number anywhere on this site is
adjusted by these factors. A park prior may only be built from earlier seasons, so 2025’s
factors can serve from 2026 onward — never for 2025 itself.
The published usage law, exactly
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Every park, highest to lowest
The bar is the park factor: how the run environment at home compared with the same team’s road games. 100 is neutral. A tall bar is not a good park or a bad one — it is a different one.
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Four seasons, side by side
One descriptive snapshot per season, each under its own usage law — four separate descriptions, never a fitted multi-year factor and never an average. A dash is a club-season this corpus does not describe, not a zero.
Season snapshots loading…
The same figures, exactly
Every park’s home and road run environment, the games each is computed over, and the Retrosheet site id it was played at.
| Team | Factor | Home R/G | Road R/G | Home games | Site |
|---|---|---|---|---|---|
| Unavailable. | |||||
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Teams
Who played here
Each team’s own page states its home environment beside its road games, and the bats that produced its value.
Open teams →Method
Why this is not an adjustment
A park prior for a season may only use earlier seasons. Using a season’s own factors to adjust that season leaks the outcome into the adjustment.
Open methodology →