<p> 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: runs per nine innings, walks per nine innings, strikeouts per nine innings, and strikeout-to-walk ratio. The statistical analysis reveals that the home plate umpire's influence on a game can be huge, both in terms of runs scored and the distribution of walks and strikeouts. By introducing umpires as individuals and encouraging a rational discussion of their work, this examination depicts umpires as dynamic actors whose impact on the game can be measured, analyzed, and enjoyed.</p>