HOW GOOD A JOB DO UMPIRES DO IN CALLING BALLS AND STRIKES? Scott Lindholm had an analysis on the SB Nation site of how accurate major league umpires have been in calling balls and strikes. His analysis is based PITCHf/x data for the years 2008 to 2013. In each of the years, between 51% and 54% of pitches required a call by an umpire. Over the six year period, 13.2% of strikes were mistakenly called balls, and 15% of balls were incorrectly called strikes. Since one eighth is equal to 12.5%. if a pitcher throws about 16 pitches in a half inning of work, about half the pitches would be called by the umpire and of those 8 pitches the umpire would call one incorrectly.
Significantly, the information for umpire performance is provided by name for each umpire.