Simkin and Roychowdhury (2002) infer from repeated identical citation misprints that citers copy references unread, estimating only about 20% read the original

citation-genealogycitation-copyingmisprintsepistemologybibliometrics

Simkin and Roychowdhury argue that an identical error in a reference is evidence about the route a citation took. For a four-digit page number there are about 10^4 possible misprints, so "the probability of repeating someone else's misprint accidentally is 10^−4"; an error that recurs is therefore inherited from an earlier reference list, not re-made independently.

Their data come from one "guinea pig" paper, Kosterlitz–Thouless 1973, cited about 4,300 times: 196 misprints, 45 distinct, the most popular one "propagated 78 times." From the misprint statistics they estimate the ratio of readers to citers at roughly 0.22–0.23 in the simple model and about 0.17 in the fuller one. The abstract's summary: "Our estimate is only about 20% of citers read the original." They say distributions for "a dozen of other studied papers look very similar," but the preprint shows only the one.

Limits worth keeping with the claim: the 20% is a model output, not a measurement; the model is the authors' own; the text read is an unrefereed preprint; and the figure describes physics citers of one famous paper, not citation behavior in general.

The method matters more than the number. Copy-inference works only when the trail carries a shared error. It is the same inference logic behind Ansari's "inherited" hallucinated reference in claim-ansari-2026-contamination-inheritance-citation-error-propagates-across-models, and its absence in a correct citation is why some trails cannot discriminate channels: see observation-copy-fingerprint-logic-explains-why-kwakernaak-1977-trail-cannot-date-song-jians-acquisition.