Year	million ton-km
1977	0.200000003
1978	0.8999999762
1979	0.8999999762
1980	0.5
1981	0.3000000119
1982	1.2999999523
1984	0.3000000119
1985	2.5999999046
1986	4.3000001907
1987	2.5999999046
1988	0.400000006
1989	0.400000006
1990	0.400000006
1991	0.400000006