Which-hunting and the Standard English relative clause: A case of institutionally backed colloquialization

In corpora of written standard English reflecting change since the 1960s, several cases of morphosyntactic variation have been shown to follow a pattern of concurrent Americanization, colloquialization, and – where one of the variants is more economical – "densification " (Leech et al. 2009). In the case of variation between which, that and zero as restrictive relativizers, a massive shift is underway from which to that. This change follows the pattern of Americanization (it is more advanced in American than in British English) and may be interpreted as a case of colloquialization (that is a less formal option than which); in addition, the enormity of the rate of change has led authors to assume (Leech & Smith 2006) that it is accelerated by the rhetoric of prescriptive grammar writing (e.g. Strunk & White 1999), which argues for the use of that and against which. Two gaps remain: (i) it has not been possible to conclusively show whether the thir