Year	% of total fuel combustion
1971	15.384615384615385
1972	9.63855421686747
1973	15.189873417721516
1974	15.068493150684931
1975	13.846153846153845
1976	16.216216216216218
1977	15.384615384615383
1978	13.043478260869565
1979	8.98876404494382
1980	8.080808080808081
1981	7.079646017699116
1982	5.426356589147288
1983	7.216494845360826
1984	7.518796992481203
1985	4.310344827586207
1986	3.7433155080213907
1987	4.591836734693878
1988	4.205607476635514
1989	3.8793103448275863
1990	3.896103896103896
1991	4.524886877828055
1992	4.6082949308755765
1993	3.558718861209965
1994	3.9840637450199208
1995	4.621848739495799
1996	4.741379310344828
1997	4.048582995951417
1998	2.5316455696202533
1999	3.319502074688797
2000	3.755868544600939
2001	3.2128514056224895
2002	3.8793103448275863
2003	3.831417624521073
2004	3.8461538461538463
2005	2.205882352941176
2006	2.3166023166023164
2007	2.1818181818181817
2008	2.3255813953488373
2009	2.42914979757085
2010	5.447470817120624
2011	3.501945525291829
2012	4.0740740740740735
2013	5.9071729957805905
2014	6.4102564102564115