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October 2, 2007

Prospectus Toolbox

The Umpires, Part I

by Derek Jacques

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Last night's one-game playoff between the Padres and Rockies was an exciting end to the regular season, made a bit more exciting by shoddy play-calling from the umps. With technology giving us detailed pitch location data, and additional cameras and high-definition television giving us a better view and more angles than ever before (except on TBS, where last night's game was presented with the same level of intensity and production values as a mid-May tilt between the Braves and Pirates), today's umpires work the playoffs under scrutiny bordering on the microscopic. In the view of some commentators, the question isn't if but when the umpires are going to have more embarrassing moments this month, and how disastrous they'll be when they happen.

Today we're going to discuss some of the tools that are used to analyze umpires' performance, and some of the research that's been based on this raw data. We'll start with the Umpires Report, located on our statistics page. The report focuses on calls made by the umpire when he's behind the plate calling balls and strikes, and essentially it gives information on every type of event that occurred in those games, including data that may seem extraneous, such as hits and home runs allowed, hit by pitch, etc. Naturally, the calls that we're going to be interested in are those on which the umpire has a direct effect: balls, strikes, walks, strikeouts, and a few others.

First, let's look at some data that could locate umpires who might have been squeezing the strike zone in 2007, with a minimum 200 innings behind the plate:


Name              G   UBB Rate (%)  Name              G    Ball %
Paul Schrieber   31      9.98       Paul Schrieber   31    40.3
Jerry Layne      19      9.24       Greg Gibson      34    40.2
Gerry Davis      35      9.24       Jerry Layne      19    40.0
Angel Hernandez  36      8.97       Gerry Davis      35    39.6
Greg Gibson      34      8.77       Jim Joyce        34    39.6
Dana DeMuth      34      8.74       Tim Timmons      33    39.4
Lance Barksdale  35      8.68       Ed Montague      31    39.4
Chuck Meriwether 33      8.54       Jerry Crawford   16    39.3
Ed Rapuano       34      8.44       Dana DeMuth      34    39.3
Mike Reilly      34      8.43       Randy Marsh      35    39.2

Some of you might remember unintentional walk rate (UBB Rate, sometimes also referred to as UBBR in our database) from the Non-Contact series. Eagle-eyed readers will note that there's no actual "Ball %" statistic in the Umpire's Report, or in its customizable version. Nonetheless, the raw data to tell us what percentage of the pitches an umpire saw were called balls is available in the report, and making this calculation on a spreadsheet is a relatively simple matter.

Now, we'll look at the opposite-umps whose strike zones might just have extended from batter's box to batter's box this season (again, with a minimum of 200 innings as the home plate ump):


Name              G   K Rate (%)   Name              G   Strike %
Andy Fletcher    18     20.0       Doug Eddings     34    46.6
Mark Wegner      33     20.0       Laz Diaz         36    45.8
Doug Eddings     34     19.6       Andy Fletcher    18    45.4
Tom Hallion      33     19.5       Bruce Froemming  33    45.3
Jeff Nelson      20     18.9       Jim Wolf         33    45.3
Laz Diaz         36     18.8       Mark Wegner      33    45.1
Chad Fairchild   28     18.8       Tom Hallion      33    45.1
Bill Miller      34     18.6       John Hirschbeck  26    45.1
Bill Welke       34     18.3       Bill Miller      34    44.9
Rob Drake        35     18.3       Bill Welke       34    44.9

If you were to calculate Ball Percentage and Strike Percentage for umps in 2007, you'd find that the numbers don't add up to 100 percent. This is because in the Umpires Report database batted balls (balls in play plus homers) are not treated as strikes. This makes some measure of sense, as an ump may not necessarily have much influence on how often the batter puts the ball in play-but we note it because it's not the way we're most accustomed to seeing things, where every pitch thrown is identified as either a ball or a strike.

The data above seems to be of substantial import to people interested in handicapping and placing wagers on baseball contests, presumably only in places where that kind of thing is legal. But the data we're looking at is raw, and doesn't seem to account for that watchword of the analytical community: context. There are no adjustments for ballpark effects, strike zone control of batters, or-most importantly-quality of pitchers. We also don't have any indication of the relative influence of the umpire, pitcher, and hitter on the strike zone of any given game.

We're going to stop here for now. A few more warnings before you go off to play with the Umpires Report:

  • It seems that this data was originally aggregated from a few different sources, because from year to year, the naming conventions for each umpire are sometimes inconsistent. For example, the fellow that heads the zone-squeezers leaderboards is listed in recent years as simply "Paul Schrieber," but for 1998 he's listed only as "Schrieber," and in some other years he goes by "schrp901."
  • The pre-fabricated Umpire Report, as linked on our statistics page, is extremely unwieldy. It contains more information than can fit on anyone's computer screen, which makes it very hard to use as-is. Hopefully, by next week we'll have a few things together to help show you how to navigate the sortable and customizable reports so that this information overload is more manageable. If you have any questions about how to use the sortable or customizable reports, now's a good time to ask.

Further Reading

Christopher A. Parsons, Johan Sulaeman, Michael C. Yates, and Daniel S. Hamermesh, "Strike Three: Umpires' Demand for Discrimination": This study from the University of Texas, which was covered in Time magazine, indicates the presence of racial bias in ball/strike calls in favor of batters and pitchers that are of the same race as the umpire, and shows an advanced use of the type of raw data contained in the Umpires Report.

Mitchel Lichtman, "A Fascinating Study…": The comments (particularly #24 and #25) to this blog post by one of the authors of The Book contain a follow-up work related to the University of Texas study on umpire discrimination.

Nate Silver, Lies, Damned Lies, "Fixing It": Inspired by the NBA referee scandal, this study looks at the possible on-the-field effect of a hypothetical attempted fix by a corrupt umpire. It's also potentially instructive for examining the effect of the bias claimed in the University of Texas study in terms of real-life wins and losses.

Dan Fox, Schrodinger's Bat, "Calling the Balls and Strikes": The next generation of baseball research is the increasingly-advanced pitch- and ball-tracking functions such as MLBAM's Pitch f/x. In this study, Dan Fox uses Pitch f/x to examine the accuracy of ball and strike calls by the men in blue.

Derek Jacques is an author of Baseball Prospectus. 
Click here to see Derek's other articles. You can contact Derek by clicking here

Related Content:  Data Use,  Racial Bias

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