Year	million ton-km
1974	1.7999999523
1975	1.8999999762
1976	1.8999999762
1977	2
1978	1.7999999523
1979	1.8999999762
1980	1.8999999762
1981	2.7999999523
1982	2.7999999523
1983	2.7999999523
1984	5
1985	4.8000001907
1986	4.8000001907
1987	4.8000001907
1988	4.8000001907
1989	3.9000000954
1990	3.9000000954
1991	3.9000000954
2019	0