Year	million ton-km
1970	5.8000001907
1971	7.0999999046
1972	8
1973	8.3000001907
1974	10.8000001907
1975	11.5
1976	13.1000003815
1977	13
1978	14.6000003815
1979	17.1000003815
1980	18
1981	21
1982	21
1983	18.7000007629
1984	17.3999996185
1985	18.3999996185
1986	16.5
1987	16.2999992371
1988	15.8999996185
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	0.441834952
2012	0.441834952
2013	1.265124
2014	0.553884
2015	0.805347336
2016	0.006442778