We address this question with annual performance and biographical data for every player over the entire history of major league baseball are aggregated to the team level for the period 1920 -- 2009 .
Major league baseball for the purposes of this study .
We address this question with annual performance and biographical data for every player over the entire history of major league baseball , which for the purposes of this study , are aggregated to the team level for the period 1920 -- 2009 .