The phenomenon of large-scale migration of Christians is the main reason why Christians' share of the population has been declining in many countries. Many Muslim countries have witnessed disproportionately high emigration rates among their Christian minorities for several generations. Today, most Middle Eastern people in the United States are Christians, and the majority of Arabs living outside the Arab World are Arab Christians. Push factors motivating Christians to emigrate include religious discrimination, persecution, and cleansing. Pull factors include prospects of upward mobility as well as joining relatives abroad. Christian emigration from the Middle East Millions of people descend from Arab Christians and live in the Arab diaspora, outside the Middle East, they mainly reside in the Americas, but there are many people of Arab Christian descent in Europe, Africa and Oceania. The majority of Arabs living outside the Arab World are Arab Christians. Christians have emigrated from the Middle East, a phenomenon that has been attributed to various causes included economic factors, political and military conflict, and feelings of insecurity or isolation among minority Christian populations. The higher rate of emigration among Christians, compared to other religious groups, has also been attributed to their having stronger support networks available abroad, in the form of existing emigrant communities. Christians had a significant impact contributing the culture of the Arab world, Turkey, and Iran. Today Christians still play important roles in the Arab world, and Christians are relatively wealthy, well educated, and politically moderate. Historical events that caused large Christian emigration from the Middle East include: 1860 civil conflict in Mount Lebanon and Damascus, Armenian genocide, Greek genocide, Assyrian genocide, 1915–1918 Great Famine of Mount Lebanon, 1923 population exchange between Greece and Turkey, 1948 Palestinian exodus, 1956–57 exodus and expulsions from Egypt, Lebanese civil war, and the Iraq war. Egypt As with most diaspora Arabs, a substantial proportion of the Egyptian diaspora consists of Arab Christians. The Copts have been emigrating from Egypt both to improve their economic situation and to escape systematic harassment and persecution in their homeland. The Coptic diaspora began primarily in the 1950s as result of discrimination, persecution of Copts and low income in Egypt. After Gamal Abdel Nasser rose to power, economic and social conditions deteriorated and many wealthier Egyptians, especially Copts, emigrated to Europe and the United States. 1956–1957 exodus and expulsions from Egypt was the exodus and expulsion of Egypt's Mutamassirun, which included the British