Figure 1 shows the growth of highway deicing salt from 1947 to 1979. Between 1965 and 1971, the growth curve was very steep and almost constant, varying slightly according to the severity of the winter and increased from 4,536,000 tons in 1965 to 9,583,984 tons in 1971. Based on this growth curve, predictions were made outside the highway field that the salt used on highways would be 15 million tons in 1975. As can be seen from the graph, highway salt usage in 1975 was slightly less than in 1971, 9,492,557 versus 9,583,984, respectively.

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