Sociolinguistic patterns in language change are largely based on generalizations from linguistic variables consisting of lexemes or morphemes. This article takes a diachronic, corpus-based approach to the diffusion of a change in a more extensive morphosemantic function consisting of several linguistic subsystems. It focuses on the pronoun variants he, they, and those used for human indefiniteness in two contexts: (a) epicene anaphoric uses with indefinite pronouns and (b) cataphoric personal references. The quantitative corpus analyses show that the pronoun selection in Early and Late Modern English developed a greater tendency to use one pronoun type over the other in both contexts. The main data come from the Corpus of Early English Correspondence and its Extension. Statistical analyses compare the observed correlations of the pronouns with a set of social, external variables and language-internal factors. This article concludes that it is possible to establish sociolinguistic patterns in larger shifts if we account for the closely related internal developments in the language.