In 1948, 65% of Israel's Jewish population consisted of immigrants; many of these 463,000 immigrant Jews had fled from persecution in Russia and, especially during the Nazi period, Central and Eastern Europe. Israel's declaration of independence publicly opened the state "to the immigration of Jews from all countries of their dispersion," and the 1950 Law of Return granted every returning Jew the right to automatic citizenship. The Nationality Law specifies other ways—including birth, residence, and naturalization—that Israeli citizenship may be acquired. In the years 1948–92, Israel took in 2,242,500 Jewish immigrants; during 1948–51, the flow was at its heaviest, averaging 171,685 per year, about evenly divided between Eastern European Jews, who were war refugees, and Oriental Jews from ancient centers of the Arab world. In the years 1952– 56, most immigrants came from French North Africa; in 1957–58 there was a renewed inflow from Eastern Europe. After a lull in 1959–60, the flow of immigrants was renewed, reaching substantial proportions by 1963, when 64,364 Jews arrived. Immigration fell to an annual average of 20,561 persons for 1965–68, rose to an average of 43,258 per year for 1969–74, then declined to an average of 24,965 for 1975–79. The number declined further to an average of 15,383 for 1980–89. As of March, 1995, around 525,000 immigrants had arrived in Israel since 1990. Most of these immigrants came from the former Soviet Union; this was the largest wave of immigration since the independence of Israel. In May of 1991, 14,000 Ethiopian Jews immigrated due to the Operation Solomon airlift. The proportion of Jewish immigrants from Europe and North America (as opposed to those from Asia and Africa) varied during the 1960s, but it rose from 40.4% in 1968 to 97.3% in 1990. (For this purpose the Asiatic republics of the USSR were counted as part of Europe). In 1984–85, some 10,000 Ethiopian Jews, victims of famine, were airlifted to Israel via Sudan. In 1992, the Jewish immigrant population was 39.4% of all Israeli Jews and 31.8% of all Israelis. A certain amount of emigration has always taken place, but the pace increased after 1975. In a typical year after 1980, about 10,000 Israelis were added to the number who had been away continuously for more than four years. From 1967 to 1992, Israel established 142 settlements in the occupied territories; about 130,000 Jews were living there by 1995. Considerable Arab migration has also taken place, including an apparent wave of Arab immigration into Palestine between World War I and World War II. During the 1948 war there was a massive flight of an estimated 800,000 Palestinians. As of 1997 there were 3.2 million Palestinian refugees living in the West Bank, the Gaza Strip, Jordan, Syria, and Lebanon under the mandate of the Gaza-based United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA). In 2000, the net migration rate for Israel was 9.1 migrants per 1,000 population. This is a significant drop from 18.7 per 1,000 in 1990. The number of migrants living in Israel in 2000 was 2,256,000. The government views the migration levels as satisfactory.