Due to increased interest in resource conservation, the recycling of raw ma terials has grown in significance in most industrialized economies. In general, recycled raw materials require a smaller net input of other basic resources, such as energy, than do the original primary materials. As a consequence the long run cost trends seem to favor an ever higher use of secondary materials over primary materials. Many of the industries currently practicing recycling are highly concentrated; i.e., aluminium, steel, newsprint, motor oil and other metals. With a few exceptions the impact of recycling on industry output and price remains largely unexplored.