Year	% of total fuel combustion
1960	23.07692307692308
1961	24.347826086956527
1962	21.7741935483871
1963	22.047244094488192
1964	21.70542635658915
1965	23.571428571428573
1966	21.333333333333332
1967	22.535211267605636
1968	19.463087248322147
1969	21.05263157894737
1970	21.969696969696965
1971	17.19681908548708
1972	16.72504378283713
1973	15.696022727272727
1974	14.716187806587245
1975	13.01739652069586
1976	15.525383707201888
1977	17.76947705442903
1978	18.899643402954663
1979	15.848214285714286
1980	16.021639617145233
1981	16.576770945702986
1982	16.84354673057172
1983	16.99499165275459
1984	15.557667934093788
1985	15.279077019020894
1986	15.892702624747619
1987	15.871222818412877
1988	15.90909090909091
1989	16.787377133988617
1990	11.988847583643123
1991	12.899758129535071
1992	13.027259684361551
1993	14.08408854553558
1994	14.516129032258064
1995	15.49212888038841
1996	15.862747855435241
1997	16.33710623210146
1998	16.353034720381658
1999	16.16960580912863
2000	16.538008635352607
2001	17.24312042413532
2002	16.684594239273334
2003	16.571874651499947
2004	17.28128041526982
2005	17.92939309797699
2006	17.862037460027405
2007	17.306238978923503
2008	19.122155881878328
2009	20.989347966429957
2010	19.717267411738586
2011	18.651301749893296
2012	18.06694448178519
2013	18.106730334903528
2014	19.03584672435105