لجنة بيل
The overall assessment of several British reports was that the increase in the Arab population was primarily due to natural increase. These included the Hope Simpson Enquiry (1930), the Passfield White Paper (1930), the Peel Commission report (1937), and the Survey of Palestine (1945). However, the Hope Simpson Enquiry did note that there was significant illegal immigration from the surrounding Arab territories, while the Peel Commission and Survey of Palestine claimed that immigration played only a minor role in the growth of the Arab population. The 1931 census of Palestine considered the question of illegal immigration since the previous census in 1922. It estimated that unrecorded immigration during that period may have amounted to 9,000 Jews and 4,000 Arabs. It also gave the proportion of persons living in Palestine in 1931 who were born outside Palestine: Muslims, 2%; Christians, 20%; Jews, 58%. The statistical information for Arab immigration (and expulsions when the clandestine migrants were caught), with a contrast to the figures for Jewish immigration over the same period of 1936–1939, is given by Henry Laurens in the following terms