Common-number pronouns, such as generic he and singular they, have a high profile in certain areas of today's linguistic research, and have been a topic for intense debate and prescriptivism for centuries. The research presented in this book focuses on corpus linguistic observations of common-number pronouns from the 16th century to the present day, investigating the processes of change in pronominal agreement patterns in two closely-related common-number structures, one anaphoric and one cataphoric. This research illustrates (dis)similarities in the variant frequencies in these structures and explores the types of sociolinguistic generalisation which can be made concerning this particular change. Using quantitative evidence of the diachronic paths of common-number pronouns, the study suggests a scale modelling the role of various social factors and language-internal constraints in language variation and change.