Recent Updates
Baseball Player Won-Loss Records
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Recent Updates to Player Won-Lost Records

Last updated January 12, 2018

Player won-lost records have been updated most recently as of January 12, 2018. The most recent update is due to the discovery of a fairly significant error in the calculation of (context-neutral, teammate-adjusted) eWins and eLosses.

Briefly, eWins and eLosses were being calculated without controlling for ballpark effects. Rather than averaging across every play within a particular ballpark, as I intended to do (and as I described in my book, I was mistakenly averaging across all plays within a particular league-season.

The last update to Player won-lost records prior to this change was on December 13, 2017. That update reflected two changes. Details of these updates can be found here. Retrosheet releases new and revised play-by-play data twice each year, usually in late June and late November. It is my intention to continue to update Player won-lost records to incorporate these new data as they become available. Because of the way in which Player won-lost records are calculated, new data may lead to updates to data which are not revised, due to possible changes in the calculation of shared credit and - for seasons for which additional data may be added - the empirical calculation of positional averages and replacement levels.

It is my sincere hope that I have not made any additional errors in the calculation of Player won-lost records so that no further adjustments of this type will be necessary. If I do find such errors, however, I will do my best to update them as quickly and completely as possible and will be sure to report any such modificiations on my website.

My apologies for having to make these corrections at this time. I hope that you will continue to enjoy these new and improved Player won-lost records and come back to my website often!

All articles are written so that they pull data directly from the most recent version of the Player won-lost database. Hence, any numbers cited within these articles should automatically incorporate the most recent update to Player won-lost records. In some cases, however, the accompanying text may have been written based on previous versions of Player won-lost records. I apologize if this results in non-sensical text in any cases.

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