_An approximately Static Distribution of Population._--The apportionment of population among the different sections of a country may be nearly normal, while migration may still go on from that country as a whole to remote parts of the general area which we include in our present study. There may be small reason for moving from one part of Germany to another and large reason for going from Germany to America. This larger movement occupies a long time, while certain other adjustments may be made more quickly. Within Germany and within the United States labor may be well apportioned among the different occupations. There may be in each country about the right comparative numbers of cotton spinners, iron workers, gardeners, wheat raisers, etc.; or in other words, the distribution of labor among the industrial groups may be approximately normal both within the one country and within the other. It may further be true that the division of occupations between the two countries in their entirety is about what, in the conditions now prevailing, economic law calls for. There are certain industries which now have their habitats in Germany and certain others that have their habitats in the United States, and this arrangement is partly due to the comparative density of the two populations. Because there are so many persons per square mile of land in Germany there is there a certain preponderance of manufacturing, and there are in America less manufacturing and relatively more agriculture. In that remote time when the relative density of the two populations shall become static, America will have reason to increase the comparative amount of the manufacturing and thus put herself in this particular more nearly on a plane with Germany. This occupation has its normal abode in regions of comparatively dense population, and a gain in comparative density means an increase in the amount of productive energy devoted to it. The place for the mill is where the land is crowded, and the better place for the work of tillage is where it is not so.[2] [2] It will appear that manufacturing reacts on the density of population, first, by retarding emigration from the thickly populated country as a whole; and secondly, by causing local movements within the country, whereby cities and villages grow, and relieve what would otherwise be an excess of labor in agricultural regions. _How an Unnatural Distribution of Population may be Treated._--So long as the slow movement of population from country to country remains incomplete, the ultimate division of occupations between the countries can never be completely static. It is therefore with a division that is only approximately static that we have first to deal, and this is realized _when in view of the comparative density of population in the different regions which now exists_ occupations are naturally apportioned.