1. Racial Bias Among MLB Umpires -- Evaluating the Evidence Phil Birnbaum www.philbirnbaum.com

2. The Hamermesh Study "Strike Three: Umpires' Demand for Discrimination" By Christopher A. Parsons, Johan Sulaeman, Michael C. Yates, and Daniel S. Hamermesh Original August, 2007; update December, 2007 New version, 2011 (not discussed here) New version

3. The Hamermesh Study Discussed in Time, USA Today, Business WeekTimeUSA TodayBusiness Week Claims to have found widespread discrimination – umpires (unconsciously) discriminate in favor of pitches of their own race Call more strikes for pitchers of the same race as them "Basically, it's an expression of deep-down preferences," says Hamermesh. "Am I sure it's there? Oh, yeah." – Business Week

4. Situations When looking at all pitches, no discrimination found But lots of apparent racial bias when QuesTec (electronic umpire checker) not in use And even more apparent racial bias when attendance is low Study claims: when umpires are not being scrutinized, they discriminate

5. Low Attendance I don't have the authors' data; I duplicated as best as I could But my results are similar to the study's

6. Low-Attendance Games White Pitchers Hispanic Pitchers Black Pitchers White Umpires 31.88 (376,954) 31.27 (107,434) 31.27 (10,471) 31.73 Hispanic Umpires 31.41 (10,334) 32.47 (2,864) 28.29 (258) 31.58 Black Umpires 31.22 (23,603) 31.21 (6,585) 32.52 (695) 31.25 31.8331.3131.2831.70

7. Is There Racial Bias? Model each cell as: Baseline % strikes Plus effect for the race of the umpire Plus effect for the race of the pitcher Plus effect if the umpire's race matches the pitcher's ("UPM") If the UPM is different from zero, there's racial discrimination

8. The Study's Conclusion After adjusting for race of umpire and pitcher, the pitch is 0.76 percentage points more likely to be called a strike if the umpire is the same race as the pitcher. Statistically significant result (Real study: 0.84, even more significant)

9. Implications Lots of discrimination apparent 0.76% of same race pitches: 1 in 130! Almost 5,000 pitches affected If only ¼ of pitches are borderline, the 1 in 130 becomes 1 in 30 Wow!!

10. The Updated Fit White Pitchers Hispanic Pitchers Black Pitchers White Umpires 31.88 31.1231.27 Hispanic Umpires 31.41 32.47 31.7128.29 Black Umpires 31.2231.21 32.52 31.76

11. But Why Those Three Cells? There are lots of other ways to modify the matrix to remove discrimination

12. How About This Instead? White Pitchers Hispanic Pitchers Black Pitchers White Umpires 31.8831.27 Hispanic Umpires 31.4132.47 30.80 28.29 30.80 Black Umpires 31.2231.21 30.61 32.52 30.61

13. Why Didn't the Study Do That? Because the authors insisted that all races of umpires must discriminate the same Hidden assumption in the regression model But why? Discrimination normally goes one way more than the other Do blacks really discriminate against whites exactly as much as whites discriminate against blacks? Doesn't seem right to me

14. Number of Pitches Affected White Pitchers Hispanic Pitchers Black Pitchers White Umpires 000 Hispanic Umpires 0 1.67% * 2864 48 -1.49% * 258 4 Black Umpires 0 -0.61% * 6585 40 1.91% * 695 14

15. Pitches Affected Total pitches affected: 106 Fewer than 1 in 4,000 Original study had 5,000 pitches affected – 43 times as many! Still statistically significant

16. Another Hidden Assumption A second hidden assumption: all umpires discriminate equally Not just that white umpires overall discriminate the same amount as black, but that every white umpire discriminates the same amount as every black umpire

17. Maybe Only a Few Umpires Discriminate It could be that a small number of umpires are responsible for the entire effect! There were only 2 hispanic umpires and 4 black umpires Look at individual umpires

18. Umpires vs. Hispanic Pitchers Individual umpires ranked by how much they appear to favor hispanic pitchers, in descending order of favorable discrimination. (X's are hispanic umps, hyphens are non- hispanic umps) ---X--------X---------------------------------- The two hispanic umps favor hispanic pitchers more than most

19. Umpires vs. Black Pitchers Individual umpires ranked by how much they appear to favor black pitchers, in descending order of favorable discrmination. (X's are black umps, hyphens are non-black umps) X--------X---------X-------------------X------- Two of the four black umps favor black pitchers more than most

20. Significance If there were no racial bias, the Xs would be balanced around the center If you remove ONE umpire... Either hispanic umpire The most extreme black umpire... then the results are no longer statistically significant! Next step: look closely at those individual umpires (review game tapes, for instance)

21. Other Years – Hardly Any Effect 2002, 2003, 2007, 2008 White Pitchers Hispanic Pitchers Black Pitchers White Umpires 31.47 (527,902) 30.97 (135894) 31.22 (14.577) Hispanic Umpires 31.19 (14,580) 30.77 (3,903) 34.65 (202) Black Umpires 30.90 (31,253) 30.07 (8,444) 32.55 (550)

22. Another Recent Replication "The Effects of Race on Called Strikes and Balls," by Jeff Hamrick and John Rasp Poster presentation at this conference, two days ago! Used not just 3 or 4 seasons of data but … 22 seasons!

23. Another Recent Replication Found weak evidence of bias when pitcher matched umpire, p=0.075 Lower significance than Hamermesh study; much more data than Hamermesh study … equals much lower coefficient So much lower estimate of bias And no effect found for attendance (p=.977)

24. Hamrick and Rask (all pitches) 1989-2010 White Pitchers Hispanic Pitchers Black Pitchers White Umpires 30.7 (5,157,716) 30.6 (1,044,030) 29.3 (247,549) Hispanic Umpires 31.7 (101,732) 31.3 (25,495) 28.8 (3,777) Black Umpires 30.8 (294,019) 30.3 (62,064) 28.7 (12,733)

25. Conclusions Effect found depends on choice of model; could be just one umpire Effect does not appear to duplicate over other seasons In my view, evidence doesn’t even come close to suggesting pervasive racial bias among umpires.