Fellegi–Sunter

Ivan Fellegi and Alan Sunter's paper 'A Theory for Record Linkage' set out the decision-theoretic basis the field still uses. Each candidate pair is treated as coming from either the matched population M or the unmatched population U. For each comparison field, two conditional probabilities are estimated: the m-probability, that the field agrees given the pair is a true match, and the u-probability, that it agrees by chance given the pair is not. The ratio of those probabilities, in logs, is the field's contribution to the score, and the contributions sum.

The result is the paper's most quoted contribution: the optimal decision rule at fixed error rates is a three-region policy. Above an upper threshold, link automatically; below a lower threshold, reject automatically; between them, refer to clerical review. Fellegi and Sunter proved this minimises the size of the review region for a given pair of error rates, which is the reason the shape persists — the middle region is the expensive one, and no policy at those error rates makes it smaller.

The framework's assumption is conditional independence between comparison fields, which is usually false: name agreement and address agreement are correlated. Practitioners handle it by modelling dependencies explicitly, by fitting weights discriminatively, or by accepting the bias and choosing thresholds empirically.

Entity Bind's scorer is Fellegi–Sunter in shape — three regions, accept, reject and a borderline band — with the weights fitted by regression rather than estimated by expectation-maximisation. The borderline band is what escalates to LLM adjudication and then to agentic research, so the review region is worked rather than merely queued.