Year	million ton-km
1970	0.6999999881
1971	0.8000000119
1972	1.1000000238
1973	1
1974	1
1975	1
1976	1
1977	2.0999999046
1978	2.2999999523
1979	2.4000000954
1980	2.5999999046
1981	2.9000000954
1982	2.7000000477
1983	2.7000000477
1984	3
1985	3.0999999046
1986	13.6999998093
1987	15.1000003815
1988	7
1989	3.9000000954
1990	4.5
1991	5.0999999046
1992	22.2999992371
1993	24.1000003815
1994	11.6999998093
1995	6.8000001907
2000	0
2001	0
2002	0
2003	0
2004	0
2005	0
2006	0
2007	0
2008	0
2009	0
2010	0
2011	0
2012	0
2013	0
2014	2.085996
2015	1.641624
2016	1.774534
2017	1.857094
2018	1.970266
2019	1.842301
2020	0.478
2021	0.312