There are three factors that together largely account for the small size of our foreign trade in synthetic resins. As a result of the comparative youth of the resin industry, the complicated patent situation, and the substantial tariff rates upon imports of resins into the United States, domestic producers have experienced little competition from abroad. The first two of these forces plus the tariff barriers of other countries have caused them to pay little attention to export markets. But it should be observed that both of the first two forces will become less important with the passage of time. When home markets have been more fully exploited, problems of production have become less pressing, and most of the basic patents on resins have expired, international trade in synthetic resins may be expected to increase from its present low levels. If this occurs, the United States, with its large scale production for the home market and with its generally favorable position with regard to the raw materials and the technical skills necessary, is more likely to become a net exporter than a net importer of synthetic resins. Rapid expansion of business in home markets. Being young industries and having potentially large home markets awaiting development, the synthetic resin industries in the United States naturally began by concentrating first on their numerous production problems to meet a rapidly expanding domestic demand, improving their products and devising useful applications. The tar-acid-formaldehyde resins for molding were the first to develop. The industry producing them may be said to have started around 1910, but did not become important until after the World War, when the drop in price of phenol made the resins available at lower prices. The alkyd resins and the urea-formaldehyde resins in the United States began to be important in 1929 and 1930, respectively. The others may be said to be still in their earliest stages of development as industries, however much research work may have been done as to their properties and production. The effect of patents on international trade. A second factor involved in limiting international trade in resins is that relating to patents. The basic patents on tar-acid resins have expired; but while they were in force, they prevented imports into the United States. In the United States a valid patent can be enforced at law not only against domestic products which infringe but also against imports. In addition to court action, the provisions of our tariff law prohibiting unfair competition in the import trade were invoked to prevent entry of synthetic phenolic (tar-acid) resin, form C, but when the basic patent for this material expired, the exclusion order no longer applied to single color material, except in the matter of certain marking requirements.[6]