Prescriptive grammar - Yenra
An article published December 2015 in the journal Language examines the impact of mass-market manuals to systematically change the way that writers use the English language. Advice books such as Strunk and White's Elements of Style, or Fowler's Modern English Usage have been able to systematically influence generation after generation of students in much of the English-speaking world. The new study demonstrates the importance of prescriptive grammar as a social force and its steady increase over the course of the twentieth century.
Linguists Lars Hinrichs and Axel Bohmann, of the University of Texas at Austin, and Benedikt Szmrecsanyi, of KU Leuven, studied 16,868 relative clauses that appeared in written publications in English from either Britain or the US, and which were published either in 1961 or in 1991/1992. In each of these cases, writers would have been able, in principle, to use either that or which as relative pronoun. The study found that there is a very significant shift from the early 60's to the 90's, in writers' preferences for that at the expense of which.