Before 1870 different parts of the small continent of Europe had specialised in their own products; but, taken as a whole, it was substantially self-subsistent. And its population was adjusted to this state of affairs.

After 1870 there was developed on a large scale an unprecedented situation, and the economic condition of Europe became during the next fifty years unstable and peculiar. The pressure of population on food, which had already been balanced by the accessibility of supplies from America, became for the first time in recorded history definitely reversed. As numbers increased, food was actually easier to secure. Larger proportional returns from an increasing scale of production became true of agriculture as well as industry. With the growth of the European population there were more emigrants on the one hand to till the soil of the new countries and, on the other, more workmen were available in Europe to prepare the industrial products and capital goods which were to maintain the emigrant populations in their new homes, and to build the railways and ships which were to make accessible to Europe food and raw products from distant sources. Up to about 1900 a unit of labour applied to industry yielded year by year a purchasing power over an increasing quantity of food. It is possible that about the year 1900 this process began to be reversed, and a diminishing yield of nature to man's effort was beginning to reassert itself.