Run expectancy
also: RE · run expectancy matrix · RE24 matrix
The average number of runs a team scores from a given base-out state to the end of the inning.
Formula
RE(outs, runners) = mean(runs from that state to the end of the half-inning)Bases empty with nobody out is worth about half a run; bases loaded with nobody out, more than two. The 24 numbers that cover every base-out state are the run expectancy matrix, and they change with the scoring environment of the season.
We build the matrix for each season from that season's plate appearances in the first eight innings. Later innings are left out because walk-offs and skipped bottom halves cut them short.
The common mistake
The matrix is a league average. A great hitter at the plate makes every state worth more than the table says, and a bad one less.
Where to get it
Related
Run expectancy from the API
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