Year	million ton-km
1970	6.4000000954
1971	7.8000001907
1972	8.6999998093
1973	9.1000003815
1974	11.6000003815
1975	12.3000001907
1976	14
1977	14
1978	15.6999998093
1979	18.2000007629
1980	19.2000007629
1981	21.3999996185
1982	21.3999996185
1983	19.1000003815
1984	17.5
1985	18.6000003815
1986	16.5
1987	16.2999992371
1988	15.8999996185
1989	18
1990	17.7000007629
1991	16.1000003815
2010	0
2011	0.778287172
2012	0.551042455537152
2013	0.456396
2014	0.471912