NBA是否於比賽吹判上偏袒明星球員？

Abstract

此篇文章以歧視經濟學為出發點，檢視在National Basketball Association (NBA)之賽場上，裁判是否會因為球員有明星之光環而給予特權，亦即吹判尺度之偏誤。抑或從forensic economics之角度來說明的話，在聯盟商業與娛樂化操作導向之時，是否犧牲了運動精神，顯著地違反了公平原則。 然而於運動領域中，要判別裁判是否有吹判之偏誤，還需考慮到場上之數據大部分是由運動員與裁判間互動產生之結果。因此方法便在於分解籃球場上之失誤(turnovers)這項數據，分成主動吹判失誤(discretionary turnovers)與非主動吹判失誤(non-discretionary turnovers)這兩種變數。 接著藉由於2007年夏季爆發出之裁判涉賭醜聞，以2006-07賽季與2007-08賽季為分隔，建構Difference-in-Differences之模型進行分析。而在所用之資料2004-2010這六個賽季當中，實證之結果確實發現裁判的吹判尺度除了顯著地存在偏袒球星之偏誤行為外，還有一般廣為所知的主場優勢，以及刻意延長季後系列賽場數之偏誤。在涉賭醜聞被公諸於世後，雖聯盟聲明賽場上之吹判是絕對地公平，但模型中除上述之發現外，藉Difference-in-Differences之設計還看出聯盟的吹判尺度在2007-08賽季產生了變化，亦即代表偏袒明星球員之現象著實存在。

In forensic economics, economic analysis uncovers evidence of hidden behavior in a variety of domains, and sports-judging is one of the topics. On the other hand, the NBA is a good place to assess discrimination: referees and players are involved in repeated interactions, with referee making decisions that might allow implicit biases to become evident. In the summer of 2007, former NBA referee Tim Donaghy was found to have bet on games that he officiated. Donaghy subsequently alleged that referee biases are rampant throughout the league. The scandal created widespread speculation about the legitimacy of controversial games in recent history, though former NBA Commissioner David Stern vehemently that Donaghy was an isolated individual in his deviance. This paper empirically examines whether there is evidence of referee biases by investigating through analysis of two main statistical categories, discretionary turnovers and non-discretionary turnovers. Furthermore, the scandal in the summer of 2007 allows me to conduct a Difference-in-Differences model. The results provide evidence that referee biases indeed exist, including referees significantly favor toward star players, home teams, and teams losing in playoff series.