The Long Shadow of Superstars: Effects on Opportunities, Careers, and Team Production

Superstars often dominate key tasks because of their exceptional abilities, but this concentration of responsibility may unintentionally limit on-the-job learning opportunities for others. Using panel data from Major League Baseball (MLB), this study examines how superstar presence affects teammates' opportunities and career outcomes. To address potential endogeneity in team composition, we exploit plausibly exogenous variation in superstar availability caused by injuries. When a superstar is active in the same team-position unit, non-star teammates play significantly less. These short-term reductions in playing time extend to longer horizons: players who begin their careers alongside a superstar who remains active for a full season (i.e., not on the injured list) are about 1.7 times more likely to exit MLB earlier than comparable peers. A key mechanism is reduced skill development -- limited playing opportunities hinder subsequent growth in offensive performance. At the team level, greater dependence on superstars raises immediate productivity but magnifies performance declines after their departure, indicating a trade-off between short-term success and long-term adaptability. Overall, the findings suggest that while concentrating key roles in top performers boosts output in the short run, it can restrict others' development and retention. Similar dynamics may arise in other organizations that rely heavily on a few exceptional individuals.