The jobs which carry the easiest opportunities for advancement in many important industries are now the subordinate positions in the various executive, administrative or sales branches. These jobs tend to be given to young men from that section of society which has affiliations, direct or indirect, with the management of industry. The growth in importance of these branches has led to the development of a specialized form of education for industrial leadership which the wage earner does not receive. Indeed, with the ever increasing complexity of the problems of business enterprise, prolonged education, itself, has become of more importance in determining individual chances of success. All these developments have greatly lessened the chances of the ordinary wage earner for any position of ownership or control. They have tended to separate the wage earners from the groups controlling industry; they have taken away in a large measure the inspiration which work receives from hopes of steady advancement. When that hope is gone only the hope for high wages is left, and that is not a sufficiently potent common aim to insure the cooperation required for so complex an activity as modern industry. Simultaneously with the revolution in industrial structure and interacting with it in many ways, there has occurred a great change in the composition and character of the wage-earning body. The change that occurred between 1870 and 1910 in the sources of the immigration which has furnished the United States with the bulk of its supply of unskilled and semi-skilled labor, is a commonplace of American industrial history. The effects of this change have been largely governed by other industrial events, chief among which may be put the increased concentration of industry in and around a relatively small number of cities or regions. For as Mr. Chapin in his study of the sources of urban increase has stated: "Immigration has been the chief source of urban increase in the United States during the past quarter of a century."[4]