"At the beginning of the century the vast majority of Jews were Yiddish-speaking Europeans, with Yiddish the main vehicle of secularization, modernization, revolution, and reform. By the end of the century, Yiddish was in daily use only among the so-called ultraorthodox while the growing majority of Jews in Israel spoke Hebrew and the shrinking minority of Jews in America spoke English."
January 1, 1970
https://en.wikiquote.org/wiki/Yiddish