ABSTRACTIn France, English is often perceived as a negative influence on the language in the eyes of purist institutions like the French Academy. Terminological commissions have been established to replace foreign expressions with French terminology that is regularly published in the Journal officiel de la République française. Although the Toubon Law of 1994 prescribes the use of this terminology in government publications, speakers are merely encouraged to do so. This article investigates the variation between English lexical borrowings and their prescribed equivalents in a large newspaper corpus containing articles from 2000 to 2017 in order to see whether formal written language complies with the purist recommendations. Time is treated with a new dynamic approach: the probability of using a prescribed term is estimated three years before and three years after official prescription. Fifty-four target terms are selected from the lexical fields of computer science, entertainment industry and telecommunication, including emblematic prescribed words such as courriel and mot-dièse. The analysis reveals that prescription is only effective when it follows already attested use. Furthermore, conservative newspapers show higher proportions of recommended terminology, especially as compared to newspapers specializing in technology.