Professor Pearl concludes that this country has passed the point of most rapid increase, that this rate began to decline about April 1, 1914, when our population was 98,637,000, and that our upper limit will be reached about the year 2100, when the population will be 197,274,000 or nearly double what it is now, with about 66 persons per square mile. Our population will be then far less dense than in many other countries, but the latter are not self-supporting. He even estimates how many calories, vegetable and animal, each individual will require daily and compares this with the agricultural possibilities of the future. Such considerations lead him to stress the importance of birth control. This had long been practiced in France before the war, where the birth- and death-rate nearly balanced, so that industrial development simply raised the standard of living. Germany, on the other hand, encouraged the increase of her population by every means and her scheme was, when the pressure became too great, to facilitate the overflow of her surplus population elsewhere. “A stationary population where birth-rate and death-rate are made to balance is necessarily a population with a relative excess of persons in the higher age groups, not of much use as fighters, and a relative deficiency of persons in the lower age groups where the best fighters are. On the contrary, a people with a high birth-rate has a population with an excess of persons in the younger age groups.” In his discussion of life tables Pearl starts with that of Glover based on the registration area of the United States in 1910. If we assume an original hundred thousand starting together at birth we note that at the beginning of the second year of life only 88,538 survive. In the next year 2446 drop out; the year following, 1062. At forty about 30,000 have passed away and the line descends with increasing rapidity until about eighty, when it drops more slowly till soon after the century mark all the original hundred thousand have passed away. Expectation of life is the mean or average number of persons surviving at a stated age. Pearl’s diagrams show that the expectation of life of those born in Breslau in the seventeenth century was very much lower than that of an individual born in the United States in 1910, the difference amounting to 18 years. At the age of ten it has sunk to 12; at twenty, to 10 years; at fifty, to 4. But the individual of eighty in Breslau in the seventeenth century could expect to live longer than the individual of the same age now in the United States. The same result is found if we compare United States tables now with those of England in the middle of the eighteenth century, where expectation was also less before and greater after eighty. Pearson’s study of Egyptian mummy cases two thousand years old shows that expectation there was far lower yet through all the early stages of life, although after seventy those who survived had a greatly increased expectation.