As some noticed in our last update to WAR. Pitchers were being significantly bumped up in value. This was due primarily to a change in our runs to win calculation. After some consultation with noted, anonymous sabermetricians Tom Tango and Patriot, we worked out a more sophisticated approach that still accounts for the player's effect on the run environment, but doesn't overvalue the contribution of stellar pitchers. We've added a new page to run through the changes we've made when converting from runs to wins. Converting Runs to Wins.
There are a few other changes that have been made as well.
Version 2.1, May 2012
- A major change to runs to win calculation. See our Runs to Wins Page for a full explanation. We now handle runs to wins calculations in an exact rather than an estimated way.
- With the change in runs to wins calculation we can now display Wins Above Average, a related win-loss % and a related win-loss% for 162 games played. We've cleaned up some of the presentation in other ways as well.
- Leverage Index adjustment is now only applied to relief pitchers.
- Leverage Index used is now the LI at the time the reliever entered the game rather than the average LI for all of their plate appearances. This is weighted by number of batters faced.
- Renamed Offensive WAR from afWAR back to oWAR. Note that oWAR + dWAR now double counts position, so adding them will not give WAR.
- Added columns for Wins Above Average (WAA), waaW-L% (effectively a rate stat for WAR), and 162waaWL%. The first W-L% is the W-L% of an otherwise average facing an average team would have in games this player played in. 162waaWL% adds enough .500 record to account for a full 162 game season (which is most applicable to pitchers).
- The adjustment for the difference in league starter and reliever ERA has been moved to the calculation of league average rather than the league replacement level.
- BUG: Fixed a park factor bug. Pitcher opponent strength was not neutralized, so a park factor was being applied to a non-park adjusted number. Now the pitcher opponent strength is converted to a neutral environment, averaged for all opponents and then park adjusted based on a custom park factor for each pitcher based on the exact parks they pitched in.
- Some feedback of version 2.0 we incorporated: Inside the Book and its readers helped immensely with the runs to wins issue.
This change has been rolled out to all of the pages. As always, your feedback is welcomed.
This entry was posted on Wednesday, May 9th, 2012 at 11:18 pm and is filed under Announcement, Baseball-Reference.com. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.