On the other hand, Malthus did not realize the extent to which new countries such as the United States, Canada, Australia, Argentina would contribute to the world’s means of subsistence. He could not predict the way in which invention would be applied in solving agricultural problems, and how today one man with improved machinery and intensive methods can produce a hundred ears of corn where one was produced a century ago. Nevertheless, the “new country” argument against Malthus’ principle of population is ultimately fallacious, for new countries soon become old, the supply of new countries becomes exhausted, and there is even a limit to soil productiveness. The very pressure of population against means of subsistence is, however, a cause of inventiveness, so that unanticipated increases in food supply may occur at any time. Socialism has criticized Malthus severely. Socialism holds that at a given time the food supply is sufficient to meet human needs but that it is poorly or unjustly distributed. With just distribution of the returns from industry, food supply would not impinge strongly on population. But socialism might greatly endanger the prudential check on population, and hence result in an increased birth rate; which in turn would more than balance any release from human misery that a just distribution of the returns from industry would effect. Another point which Malthus did not observe is that the increase in technical skill which comes with vocational education is overcome by the tendency of the world’s population to overtake the world’s food productiveness. With increase in population, the price of land rises, the rent for land increases, the cost of living mounts upward, and the purchasing power of the dollar, or its equivalent, declines. Some of the followers of Malthus have advocated birth control as an artificial means of regulating population. Birth control prevents by physical means the birth of children. It is a useful weapon against sexually brutal husbands. It does not provide for self control or moral control of the sexual impulses. It encourages rather than controls gratification of the sexual desires. By it a gain is made in protecting helpless women and in cutting down the birth rate among the lower moral classes, whether wealthy or poor, but the gain is more than lost by the opportunity which birth control gives to the irregular gratification of sexual impulses and by the resultant weakening of moral fibre.