This is an estimate based on the quarter million estimate of Colognian speakers published 1997 by H. Jakobs according to http://www.ethnologue.com/show_language.asp?code=ksh or in print in: M. Paul Lewis (editor): Ethnologue: Languages of the World. 16th edition, ISBN978-1-55671-216-6. There is no language census about Ripuarian speakers.