資訊不對稱為經濟學所關注的現象，而其中的代理人問題所導致的道德風險則是具有代表性的議題之一。然而職業運動中是否存在此現象？本研究藉由合約剩餘年數與球員績效的關係，檢驗近十年大聯盟於自由市場簽約的野手是否存在簽約後的懈怠效果（shirking effect）？進一步驗證代理人問題是否存在於近十年美國職棒的自由球員市場。 過去的研究結論依研究方法等不同，對於懈怠效果存在與否有不一致的結論。本研究則蒐集2012-2021球季於自由市場簽約的野手球員資料作為研究樣本，使用最全面的球員績效指標：勝場貢獻值（WAR），並以固定效果與隨機效果模型，來探討連續型與類別型的合約剩餘年數，對球員績效的影響。並進一步將球員依照守備位置劃分為內野手及外野手，探討不同守備位置的球員，其合約剩餘年數對球員績效的影響。 實證結果顯示球員的績效與合約剩餘年數呈現顯著的負向關係；若以球員預期與實際績效的差異值（GAP）作為被解釋變數：得到剩餘合約年數越高，球員實際績效越低於預期水準的顯著結果。兩種方式皆顯示出球員存在簽約後的懈怠效果。若進一步將球員以守備位置做劃分，則實證的結果顯示出內野手及外野手在懈怠效果上存在差異：相比於合約剩餘一年時的表現，內野手合約剩餘4-5年時的表現顯著降低；而外野手合約剩餘2-3年與合約剩餘6年以上時的表現則顯著降低。 本研究的貢獻除了驗證了近十年於大聯盟自由市場簽約的野手存在懈怠效果以外，也發現內野手及外野手在懈怠效果的表現上存在差異。在球隊簽約政策方面，本研究也依據實證結果，提出針對不同位置的球員合約中，給予激勵條款或球員選擇權，來降低球員產生懈怠行為的誘因。 ;Information asymmetry is a topic discussed in economics, and the moral hazard caused by the principle-agent problem is one of the representative issues. This study uses the relationship between the remaining years of the contract and the performance of the players to test whether the fielders who signed in the free agent market in the major leagues in the past ten years have the effect of shirking, to verify whether the principle-agent problem exists in professional baseball in the past ten years. Past research conclusions are inconsistent according to the research method, This study collects fielders who signed in the free agent market during the 2012-2021 season as a research sample, and use the player performance indicator WAR to discuss the impact of the remaining years of the contract on performance. To test whether the fielder free agents signed in the past ten years have the effect of shirking after signing. Furthermore, the players are divided into infielders and outfielders, and the influence of the remaining years of contract of players in different positions on the performance of players is discussed. The empirical results show a significant negative relationship between the player’s performance and the remaining years of the contract. If the player’s performance is replaced by the difference between the player’s expected and actual performance (GAP), the results show that the higher the number of remaining contract years, the higher the gap between performance and expected level, both shows that the shirking effect is exist, the hypothesis of the principle-agent problem is confirmed. In addition to verifying the shirking effect of fielders who signed in the major league free market in the past ten years, the contribution of this research also found that infielders and outfielders have differences in the performance of shirking effect, if players are divided into infielders and outfielders, the infielder’s performance of the remaining 4-5 years of the contract is lower than the performance of the contract year; Outfielder’s performance for the remaining 2-3 years of the contract and the remaining 6+ years of the contract is lower than the performance of the contract year. In terms of team signing policy, this research also proposes incentive clauses or player options in player contracts for different positions to reduce the incentives for players to shirk.
