Expected Win-Loss Record (X W-L)

by Chris on April 9, 2007

Major League Baseball now posts (since mid-2006) a new stat:

X W-L – Expected won-loss record based on runs scored (RS) and runs allowed (RA), using this formula: RS^1.82/((RS^1.82)+(RA^1.82))

… what does this tell us?

Seemingly this stat can tell you how teams win, if the X W-L ratio greater than the actual W-L ratio the team loses close games but wins big, or if less than the team is winning close but losing big.


for the real math behind it, check out this 1999 article form Baseball Prospectus

In practical terms, the implications are fairly small. For most off-the-cuff calculations of runs and runs allowed into wins, the 1.5% gain in accuracy isn’t worth the trouble of finding a new exponent for every team; just use 1.85 or thereabouts, and get on with your life.

It really makes a difference, though, to the small group of people who try to assess the value of a player’s performance as precisely as possible.

The most noticeable impact is going to be on the value of good pitchers in extremely pitching-friendly environments. A pitcher-friendly environment brings down the exponent; a good pitcher, by his own efforts, decreases the run environment and the Pythagorean exponent even further.

continue on for a good Bob Gibson example

Honestly, I don’t see how this helps anyone understand anything.

[tags]MLB, baseball, stats, X W-L[/tags]

{ 3 comments… read them below or add one }

Brian May 29, 2011 at 6:00 AM

I agree with Chris… this one doesn’t mean much to me. Maybe we should rename it from ‘ExWL’ to ‘WTF’. 🙂

Frank Anthony August 29, 2011 at 11:33 PM

I don’t know why they bother posting this stat. Seems pointless.

FABBAQ September 20, 2017 at 8:28 PM

The most senseless stat

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