Year	million ton-km
1970	3.5999999046
1971	3.7000000477
1972	3.2000000477
1973	3
1974	3
1975	3
1976	5.0999999046
1977	4.1999998093
1978	3.4000000954
1979	3.2999999523
1980	3.7999999523
1981	3
1982	2.7000000477
1983	1.8999999762
1984	2.2000000477
1985	2
1986	2.2000000477
1987	2.5
1988	2.2999999523
1989	2.7999999523
1990	4.3000001907
1991	3.0999999046
1992	1.7999999523
1993	17.5
2010	2.248762813
2011	1.83021841731528
2012	2.04647355444776
2013	1.97274
2014	0.851628
2015	0.50237232
2016	0.399566257
2017	0.229947
2018	0.44987
2019	1.149492
2021	1.021922