Some people outside of the steel industry have said we could meet all our future ore needs entirely with . . magnetic and non-magnetic taconites, but many of us in the steel industry who have the responsi bility of operating the properties think otherwise. . . the talk of America's inexhaustible resources is over. At one time we had enough raw materials to take care of many of our needs and to supply other parts of the world; but that is no more.(36) Markets for metals have become more international as shipping capacities have risen and transportation 37 costs fallen, especially during the past twenty years. Since higher grade foreign ores may be substituted for domestic ores until their acquisition costs become equal at the margin, one would expect tendencies toward increasing costs of domestic mining to be mitigated by and reflected in increased ore imports. That, in fact, is what has happened. The burden of increasing costs has not been as apparent as it might have been because the United States has begun to tap not only its own resources, but those of the rest of the world as well. Richards, Iron Ore Outlook, p. 12; p. 22. Mr. Richards was vice president of Republic Steel Corporation at the time this address was presented. 37 Reductions in shipping costs helped to increase the average length of voyage of sea-borne ore from 1,900 miles in 1950 to more than 3,000 miles in 1967. Of. Mining Annual Review (London: The Mining Journal Limited, 1967), p. 39*