Year	million ton-km
1970	5.8000001907
1971	7.0999999046
1972	8
1973	8.3000001907
1974	10.8999996185
1975	11.6000003815
1976	13.1999998093
1977	13.1000003815
1978	14.8000001907
1979	17.2999992371
1980	18.2000007629
1981	21.1000003815
1982	21.1000003815
1983	18.7999992371
1984	17.3999996185
1985	18.3999996185
1986	16.5
1987	16.3999996185
1988	16
1989	18
1990	17.7000007629
1991	16.1000003815
1992	15.1999998093
1993	14.1999998093
1994	14.3999996185
1995	15.3000001907
1996	16.3999996185
1997	15.3000001907
1998	13.5
1999	13.6999998093
2000	12.273
2001	7.364
2010	0
2011	0
2012	1.46578302
2013	1.080708
2021	0.75585912