The University of Michigan study, led by Jimin Song with senior author Richard Paulsen, compares KBO player performance before and after the league introduced the Automated Ball-Strike (ABS) System. Researchers matched outcomes from 2023, the final season with human ball-and-strike calls, to results from 2024, the first season using ABS. The ABS uses cameras and pitch-tracking technology to determine whether a pitch crosses the strike zone; the system relays the call to the home plate umpire.
After ABS, high-status hitters showed a clear reduction in the advantage they had previously enjoyed. Compared with lower-status batters, famous hitters walked less, struck out more and reached base less often. The paper notes that, out of 100 at bats under ABS, a famous batter had nearly three more strikeouts and nearly two fewer walks than a lesser-known hitter. Because broader hitting measures changed little, the authors say the effect likely reflects changes in strike-zone judgments rather than a drop in batting talent.
The same pattern did not appear among high-status pitchers. Song offers possible explanations: pitchers may not have had enough opportunities to reveal similar effects, or pitcher performance may simply be more variable. The study places the results in the context of the Matthew Effect, arguing that established status is often reproduced and that automated evaluation can reduce favoritism in areas such as hiring or promotion. Major League Baseball implemented the Automated Ball-Strike Challenge System this year, though there is no timeline for fully automated calls; ABS has been generally accepted in the KBO while MLB’s rollout has been more divisive.
Paulsen notes the team did not test whether reputation-based calls affected game outcomes, but he suspects they have swayed results. He adds that human judgment still matters for more subjective decisions, for example:
- foul calls in basketball
- pass interference in football
- penalty calls in hockey
- card decisions in soccer
Difficult words
- automated — done by machines or computer systems
- strike zone — area a pitch must cross for strikesstrike-zone
- favoritism — unfair support for certain people
- rollout — organized introduction of a new system
- divisive — causing disagreement and strong opinions
- reputation-based — decisions influenced by a person's public standing
- judgment — decision made using personal evaluationjudgments
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Discussion questions
- What are the possible benefits and drawbacks of using automated systems like the ABS in sports? Give reasons.
- How could reduced favoritism from automated evaluation affect hiring or promotion in other fields?
- Which of the subjective calls listed (foul calls, pass interference, penalty calls, card decisions) do you think should remain with human judgment, and why?
