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	Gwet's AC1	Intercoder Reliability
Field	Communication	Communication
Family	Process / pipeline	Process / pipeline
Year of origin	2008	1960
Originator	Kilem L. Gwet	Foundational coefficients by Cohen (1960) and Krippendorff (1970)
Type	Chance-corrected agreement coefficient robust to the prevalence paradox	Procedure and coefficients for certifying coding agreement
Seminal source	Gwet, K. L. (2008). Computing inter-rater reliability and its variance in the presence of high agreement. British Journal of Mathematical and Statistical Psychology, 61(1), 29–48.	Hayes, A. F., & Krippendorff, K. (2007). Answering the call for a standard reliability measure for coding data. Communication Methods and Measures, 1(1), 77–89.
Aliases	Gwet AC1, AC1 coefficient, Gwet's first-order agreement coefficient, Gwet AC1 Katsayısı	Inter-rater reliability, Coder agreement assessment, Reliability of coding, Kodlayıcılar Arası Güvenirlik
Related	4	4
Summary	Gwet's AC1 is a chance-corrected agreement coefficient introduced by Kilem Gwet in 2008 as a robust alternative to Cohen's and Fleiss' kappa. It targets the kappa paradox — the unsettling result where coders agree on the vast majority of units yet kappa is near zero because one category dominates — by estimating chance agreement in a way that does not collapse when category prevalence is extreme.	Intercoder reliability is the degree to which independent coders, applying the same coding scheme to the same content, arrive at the same coding decisions. In content analysis it is the central guarantee that findings reflect the messages rather than the idiosyncrasies of who happened to code them, and reporting a chance-corrected reliability coefficient is a near-universal requirement for publication in communication research.