The term "the 100 most-cited statistical papers" is used to define "citation classics." I thought my foreign-speaking client was using the hyphen incorrectly, but this is how it is termed by the native English scholars of the field. What is the justification for using this hyphen with the superlative?
The assertions about usage made in this answer are made from comparisons using Google Books Ngram Viewer. Simple Google searches were made to get a subjective feel of whether Ngram results were typical of general contemporary usage.
Both are used in general
The assertion in the question that “most-cited… is how it is termed by the native English scholars of the field” is a little misleading in a general linguistic sense. The term “Citation Classic” was introduced by Eugene Garfield in his publication “Current Contents”, and in relation to this he used the adjectival phrase “most-cited” in a hyphenated form. However in the same general context the unhyphenated form is also found, e.g. Journals of the Century, Cole and Stankus, 2014 has:
By 1995 the Harvard Law Review had published 42 of the 102 most cited law review articles of all-time
So one might ascribe the justification as:
The whim of Eugene Garfield.
Readability and removal of ambiguity
My initial response was that the justification was:
For readability and to avoid “false scent”
You have a noun, papers, with four preceding words qualifying it. As most and cited form a pair (you could formerly replace them with a single superlative like “greatest”) then hyphenating them makes it clear they go together and reduces the number of qualifiers to three.
However, on reflection I do not think this stands up very well. You could argue that “most” can only qualify the single word “cited” as it would make no sense qualifying “cited statistical”, and that “100” cannot qualify “most” alone, so that in reality there is no “false scent”. That leaves readability, but ‘most-cited’ is also used when there is no preceding qualifying number i.e. less possibility for ambiguity. Anyway, we punctuate, but don’t generally hyphenate, for readability.
Furthermore, other adjectival phrases with most are not hyphenated. I could find no examples of “most-beautiful women” or even “most-beautiful”. Using an adjectival participle of the same type and number of syllables, “hated”, one can find a few examples of “most-hated men”, but these are vastly outnumbered by “most hated men”.
So I conclude that there is no general grammatical justification, but that there is something special about ‘most-cited’
Transition to a concept in its own right
There is a well-known linguistic change from “Adjective Noun” to “Adjective-Noun” to “AdjectiveNoun”, as the adjective and noun become more closely associated with one another in the minds of users. Perhaps that is what has happened in this case, and
‘Most-cited’ has developed into an adjective in its own right rather than being an example of the use of a general superlative
(However, I don’t anticipate a further transition to “mostcited”. But who knows…)
I'd put those hyphens down to ignorance. A small minority of writers hyphenate most + [past participle used adjectivally], but the vast majority don't (and never did)...
...and nobody hyphenates most + [standard adjective]...
By way of further illustrating how "nonsensical" the cited hyphen usage is, it's worth noting that nobody includes it unless the actual number of "most-verbed" entities is explicitly specified ...
I defy anyone to come up with a convincing rationale as to why the presence or absence of a specific number (one of the N most wanted criminals) should make any difference to the orthography.