In 1982 The US Corps of the Engineers published this information to the members of Upper Mississippi Waterways Towing Association. It took the years 1974- 1980 and represented tons of grain to Gulf by Barge. They then provided a prediction for 1985. Compute their estimate
There are 2 problems with this analysis, Briefly, What are they? It has nothing to do with "short" list of data. The real data goes back to 1939. I don't provide you ALL the data because there is nothing gained by making you examine 40 years of data.
1974 24
1975 31
1976 34
1977 39
1978 42
1979 47
1980 53