Year	% of total fuel combustion
1971	12.234739324076502
1972	12.149055640632973
1973	10.836363636363634
1974	9.745093616061355
1975	10.904255319148936
1976	10.139787189651575
1977	10.567475436133947
1978	10.561708860759492
1979	10.382106244175207
1980	10.684833273574757
1981	11.083569405099151
1982	10.500424088210346
1983	9.193394728485234
1984	8.987903843209308
1985	9.451970443349753
1986	9.622393934975944
1987	9.58134307389716
1988	9.696073157611618
1989	12.914085645030971
1990	7.923521565140062
1991	7.811654338805702
1992	9.008654602675058
1993	9.949622166246852
1994	10.721757322175733
1995	10.923487883991603
1996	11.7925370469559
1997	12.108717603500507
1998	11.329778892896348
1999	10.954545454545455
2000	10.644816530103311
2001	10.684440907282134
2002	10.843069150615724
2003	10.767750856730597
2004	11.259031689139217
2005	11.35436567356844
2006	10.998623943385098
2007	10.305869385505648
2008	10.231549121175897
2009	10
2010	9.65246121032161
2011	9.213083571103668
2012	8.730773938231815
2013	8.725548310610552
2014	8.88501742160279