Year	million ton-km
1970	0.1000000015
1971	0.1000000015
1972	0.1000000015
1973	0.1000000015
1975	0.200000003
1976	0.200000003
1977	0.200000003
1978	0.200000003
1979	0.200000003
1980	0.200000003
1981	0.6000000238
1982	0.6999999881
1983	0.6000000238
1984	0.6999999881
1985	0.6000000238
1989	0.400000006
1990	0.400000006
1991	2.0999999046
1992	0.6999999881
1993	0.6999999881
1994	1.3999999762
1995	0.6999999881
1996	0.6999999881
1997	0.6999999881
1999	1.3999999762