Opposing Pitchers Sharing a Birthday

In a group of 25 people (such as a baseball club), there is a 57% chance that at least two people will share a birthday. In a group of 50 people (such as competing ballclubs), there is a 97% chance of at least two people sharing a birthday. Given this, how often have opposing pitchers shared a birthday?

With the Retrosheet database providing the AL/NL starting pitcher logs through 2014, we have pitching matchups for roughly 200,000 games. The Lahman Baseball Database has complete birthdates for approximately 18,100 players (97% of all in history). A match of the Retrosheet player IDs for both pitchers in each game with the ID (and birthdates) in Lahman yields the following:

Game date Birth Month/Day vteam vlg hteam hlg Vis Name Vis Birth Year Home Name Home Birth Year
19980903 4/26 ARI NL PIT NL Anderson 1972 Cordova 1972
20120624 3/6 WAS NL BAL AL Detwiler 1986 Arrieta 1986
20020608 11/7 MIL NL PIT NL Rusch 1974 Benson 1974
19900603 8/4 BOS AL CLE AL Clemens 1962 Farrell 1962
20090928 4/15 CHA AL CLE AL Danks 1985 Laffey 1985
20100911 9/9 KCA AL CHA AL Davies 1983 Jackson 1983
19950503 11/24 MIL AL BAL AL Eldred 1967 McDonald 1967
19920921 10/19 BOS AL DET AL Gardiner 1965 Haas 1965
19170818 1/16 SLN NL NY1 NL Goodwin 1891 Schupp 1891
19150924 7/31 BSN NL PIT NL Nehf 1892 Kantlehner 1892
19220507 10/1 SLA AL CLE AL Kolp 1894 Mails 1894
20000530 12/31 TEX AL DET AL Loaiza 1971 Moehler 1971
20000523 12/24 ATL NL MIL NL Millwood 1974 Wright 1974
19340518 8/11 BOS AL SLA AL Rhodes 1907 Newsom 1907
19650504 10/7 WS2 AL KC1 AL Ortega 1939 O’Donoghue 1939
19630526 11/17 KC1 AL LAA AL Pena 1933 Osinski 1933
  • Finally, there has been precisely one game that was played on the birthday of both pitchers.  On May 3, 2012, Ryan Dempster (born 5/3/77) faced off against Homer Bailey (born 5/3/86).

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