The answer to why there was so little assimilation of Jews in central and eastern Europe for so long would seem to lie in part in the probability that the alien surroundings in central and eastern Europe were not conducive, though contempt did not prevent some assimilation. Furthermore, Jews lived almost exclusively in shtetls, maintained a strong system of education for males, heeded rabbinic leadership, and scorned the life-style of their neighbors; and all of these tendencies increased with every outbreak of antisemitism.

The lack of assimilation of Jews in central and eastern Europe lies in part to the fact that they lived almost exclusively in what?