Actually the Anglo-American Committee Of Inquiry (1946-47) was very clear and detailed on this

Submitted by Dani (Italy), Aug 6, 2016 at 11:43

The Anglo-American Committee of Inquiry, 1946-47, was very clear and detailed on this:

That each [temporary migration into Palestine] may lead to a residue of illegal permanent settlers is possible, but, if the residue were of significant size, it would be reflected in systematic disturbances of the rates of Arab vital occurrences. No such systematic disturbances are observed. It is sometimes alleged that the high rate of Arab natural increase is due to a large concealed immigration from the neighbouring countries. This is an erroneous inference. Researches reveal that the high rate of fertility of the Moslem Arab woman has remained unchanged for half a century. The low rate of Arab natural increase before 1914 was caused by:

(a) the removal in significant numbers of men in the early nubile years for military service in other parts of the Ottoman Empire, many of whom never returned and others of whom returned in the late years of life; and

(b) the lack of effective control of endemic and epidemic diseases that in those years led to high mortality rates" (Anglo-American Committee Of Inquiry, 1946-47).

For a more academic approach on these issues:
http://storicamente.org/kamel_middle_east_migrations

Note: Opinions expressed in comments are those of the authors alone and not necessarily those of Daniel Pipes. Original writing only, please. Comments are screened and in some cases edited before posting. Reasoned disagreement is welcome but not comments that are scurrilous, off-topic, commercial, disparaging religions, or otherwise inappropriate. For complete regulations, see the "Guidelines for Reader Comments".