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Who Gains When the Umpire Is a Machine? Evidence from the Automated Ball-Strike System (ABS)

Seung Jin Cho, Jun Yeong Lee · 2026 · arXiv (Cornell University)

DOI: 10.48550/arxiv.2610.27576 · cited by 0 works (OpenAlex) · open-access PDF

Indonesian

Pada tahun 2024, Organisasi Baseball Korea menjadi liga top-tier pertama yang menggantikan penilaian bola dengan sistem otomatis. Menggunakan lebih dari satu juta pitch dari 2021 hingga 2026, kami memisahkan perubahan ke penghapusan kebijaksanaan manusia dan penetapan geometri zona baru. Mesin ini menghilangkan panggilan yang tergantung pada hitungan, nilai frame catcher dan keuntungan kecil untuk batter bintang, sewa hanya bernilai beberapa kali per musim pemain. Karena mesin zone scales dengan ketinggian dan memperlakukan setiap matchup sama, itu mendistribusikan serangan ke arah batter tinggi dan di seluruh matchups, tetapi beberapa pitch terpapar dengan perubahan ini, dan efek mereka pada hasil penampilan papan diperkirakan dengan tepat dan dekat dengan nol. Pitchers dioptimalkan kembali dengan cepat melempar lebih tinggi, dengan tangan kirinya menangkap tren yang ada, di mana kita menemukan bukti bahwa batter tidak

Machine translation (Meta M2M100); the English original follows.

Abstract

In 2024 the Korea Baseball Organization became the first top-tier league to replace the home-plate umpires ball-strike judgment with an automated system. Using over a million pitches from 2021 to 2026, we separate the change into the removal of human discretion and the imposition of a new zone geometry. The machine eliminated count-dependent calls, the value of catcher framing and a small advantage for star batters, rents worth only a few runs per player-season. Because the machines zone scales with height and treats every matchup alike, it redistributed strikes toward tall batters and across matchups, but few pitches are exposed to these changes, and their effects on plate-appearance outcomes are precisely estimated and close to zero. Pitchers re-optimized quickly by throwing higher, with left-handers catching up to an existing trend, whereas we find no evidence that batters adjusted. The results suggest that the incidence of replacing human judgment with a rule depends on its geometry and on exposure.

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Topics: League, Economics, Discretion, Computer science, Throwing, Boom

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