xFIP Seasonal Adjustment

I made a change last night to xFIP that adjusts the major league HR/FB rate on a seasonal basis. Previously, the average was set at 10.5%. In recent years the average HR/FB has been somewhat lower than 10.5%, which is what prompted the change.

2007 – 9.7%
2008 – 10.1%
2009 – 10.1%
2010 – 9.4%

Overall a player’s 2010 xFIP will tend to be a little bit lower, at most around 0.20 runs, but generally more in the 0.05 to 0.10 range.

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David Appelman is the creator of FanGraphs.

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Mike Green
Guest
Mike Green

David, what HR/FB rate are you now using? I am guessing that you are using the league average over the 2007-10 period.