Counting on Consensus: Selecting the Right Inter-Annotator Agreement Metric for NLP Annotation and Evaluation

Joseph H. F. James


Abstract
Human annotation remains the foundation of reliable and interpretable data in Natural Language Processing (NLP). As annotation and evaluation tasks continue to expand, from categorical labelling to segmentation, subjective judgment, and continuous rating, measuring agreement between annotators has become increasingly more complex. This paper outlines how inter-annotator agreement (IAA) has been conceptualised and applied across NLP and related disciplines, describing the assumptions and limitations of common approaches. We organise agreement measures by task type and discuss how factors such as label imbalance and missing data influence reliability estimates. In addition, we highlight best practices for clear and transparent reporting, including the use of confidence intervals and the analysis of disagreement patterns. The paper aims to serve as a guide for selecting and interpreting agreement measures, promoting more consistent and reproducible human annotation and evaluation in NLP.
Anthology ID:
2026.lrec-main.347
Volume:
Proceedings of the Fifteenth Language Resources and Evaluation Conference
Month:
May
Year:
2026
Address:
Palma de Mallorca, Spain
Editors:
Stelios Piperidis, Núria Bel, Henk van den Heuvel, Nancy Ide, Simon Krek, Antonio Toral
Venue:
LREC
SIG:
Publisher:
ELRA Language Resource Association
Note:
Pages:
4434–4446
Language:
URL:
https://preview.aclanthology.org/ingest-lrec/2026.lrec-main.347/
DOI:
Bibkey:
Cite (ACL):
Joseph H. F. James. 2026. Counting on Consensus: Selecting the Right Inter-Annotator Agreement Metric for NLP Annotation and Evaluation. International Conference on Language Resources and Evaluation, main:4434–4446.
Cite (Informal):
Counting on Consensus: Selecting the Right Inter-Annotator Agreement Metric for NLP Annotation and Evaluation (James, LREC 2026)
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PDF:
https://preview.aclanthology.org/ingest-lrec/2026.lrec-main.347.pdf