Israel's population is overwhelmingly urban with heavy concentrations in the kibbutz, moshav and kibbutzim. The increase in the non-Jewish population was a result of high birthrates; the increase in the Jewish component was due primarily to immigration. The concept of unlimited immigration has been reinforced by the programs and actions of successive governments and has had overwhelming support in parliament and from Israel's Jewish population. Mass immigration was a special case that resulted from the substantial reservoir of Jews anxious to immigrate to Israel and from the unusual efforts made by Israeli and Zionist authorities to bring the largest possible number of Jewish immigrants to Israel in the shortest amount of time. The Jewish community in Palestine prior to the waves of Zionist immigration was concentrated in a number of important cities, notably Jerusalem, and focused on religious interests and activities.