A standard of living, once established, has great tenacity, and people will suffer almost anything in the way of hardship before they will reduce it. If, for any reason, the dilemma is presented to a people of lowering their standard or of limiting their rate of increase, they will in general adopt the latter alternative. This will come about, not so much as the result of a conscious choice, as by the unconscious adaptation to surrounding conditions.[271] On the other hand, if natural conditions are gradually and steadily improving, it may frequently happen that the rate of reproduction will keep pace therewith, so that the standard of living will remain essentially the same. But if some sudden improvement in conditions appears—like the opening up of great stretches of new land, or some far-reaching improvement in the arts—the standard of living may rise appreciably before the forces of reproduction have had time to offset the new advantage. In other words, the rise of standards of living does not take place ordinarily by a steady and unvarying progress, so much as by successive steps or waves. The regular, continuous improvements in conditions account for lifted standards less than the exceptional, epochal occurrences. Such occurrences, being inherent in the cosmic laws and in the constitution of human nature, transpire with sufficient frequency to make possible great advances in standards of living over long periods of time. Let us apply these principles to the case of the United States, and seek to determine what part immigration has played in their operation.[272] At the beginning of its career the United States was most favorably circumstanced as regards its standard of living. A people whose knowledge of the arts represented the highest product of the civilization of the day was set down in a practically uninhabited country, apparently unlimited in extent, and of marvelous fertility and abundance of natural resources. All of the old checks to population were removed, and there resulted a natural increase of numbers unprecedented for a corresponding area and extent of time in the annals of the race. But even this could not keep up with the development of natural resources, and a general standard of living was established far ahead of any other nation of the period.