As a factor in lowering the cost of distribution of trade marked commodities from manufacturer to consumer, Outdoor Advertising, through its nation-wide scope and its high efficiency, is constantly becoming more important in the American economic structure. The large amount of capital invested, the number of people employed in the business, and the fact that Outdoor Advertising is a substantial consumer of the products of other lines of business, such as lithography, steel, lumber, paper, paint, electric current, etc., make this in itself an industry which ranks high in national importance.