Year	million ton-km
1978	0.1000000015
1979	0.1000000015
1980	0.200000003
1981	0.200000003
1982	0.3000000119
1983	0.3000000119
1984	0.400000006
1985	0.400000006
1986	0.3000000119
1987	0.3000000119
1988	0.3000000119
1989	0.1000000015
1990	0.1000000015
1991	0.1000000015