AT the World Population Conference held at Geneva in 1927, one might observe a contrast in viewpoint of the very greatest interest. The delegates from the United States were much concerned with the imminence of the dangers of over-population, while the majority of European speakers, at least those who spoke with authority on their own national statistics, pointed out in almost monotonous succession that their birth rates either had already fallen or would soon fall below the level necessary to maintain stationary populations. Generally speaking, northern Europe has seen the end of the period of population expansion. Is it possible that the American average of 39 to the square mile is more impressive of over-population than the European average of about 300? (1) The Balance of Births and Deaths. Vol. 1: Western and Northern Europe. By Robert R. Kuczynski. (The Institute of Economics of the Brookings Institution.) Pp. xii + 140. (London: George Allen and Unwin, Ltd.; New York: The Macmillan Co., 1928.) 10s. net. (2) The Shadow of the World's Future: or the Earth's Population Possibilities and the Consequences of the Present Rate of Increase of the Earth's Inhabitants. By Sir George Handley Knibbs. Pp. 131. (London: Ernest Benn, Ltd., 1928.) 10s. 6d. net.