Lack of assimilation may occur wherever there are minority groupings of a racial, religious, ideological or linguistic kind. The groups may be immigrant or indigenous. It is aggravated by social inequalities and exploitation which create ethnic conflict. Since ethnic differences may be very great, assimilation means that at least one group must give up some of its customs, which it may be very unwilling to do. Where there is extensive segregation and little intermarriage, ethnic purity is likely to remain intact and prejudices and discrimination persist.