Thirty years into baseball's sabermetric revolution, relatively little attention has been paid to the impact of a major league umpire's ball-and-strike judgment on game results. This welcome study corrects this omission by profiling more than ninety current umpires, summarizing their professional history, and charting their performance at home plate from 2007 through 2010. Annual and four-season rankings place the umpires according to four categories:...