Year	% of total fuel combustion
1971	3.0534351145038165
1972	4.132231404958678
1973	4.615384615384615
1974	3.787878787878788
1975	3.389830508474576
1976	4.237288135593221
1977	5.128205128205128
1978	5.6000000000000005
1979	3.787878787878788
1980	5.925925925925926
1981	4.026845637583892
1982	5.925925925925926
1983	8.275862068965518
1984	7.4074074074074066
1985	6.474820143884894
1986	6.707317073170732
1987	6.989247311827956
1988	7.253886010362695
1989	6.896551724137932
1990	5.529953917050691
1991	5.882352941176471
1992	17.26618705035971
1993	18.888888888888886
1994	18.84057971014493
1995	19.396551724137932
1996	20.463320463320468
1997	21.090909090909093
1998	18.83561643835617
1999	17.808219178082194
2000	17.5
2001	19.05940594059406
2002	18.764845605700714
2003	24.288840262582056
2004	20
2005	17.59465478841871
2006	17.5
2007	17.25417439703154
2008	16.35434412265758
2009	15.525876460767945
2010	14.76510067114094
2011	12.663755458515283
2012	13.480055020632738
2013	11.411764705882353
2014	10.952902519167578