Year	% of total fuel combustion
1971	3.472239215014559
1972	3.3916999862126023
1973	3.276023757424195
1974	3.4116320028496228
1975	3.5066247037339235
1976	3.4942428535105874
1977	3.333854248059593
1978	3.2577581159325995
1979	3.3642779835673235
1980	3.4718561471328995
1981	3.340993716546427
1982	3.4588655958937684
1983	3.4162999161012086
1984	3.3238380373804612
1985	3.7714253011703436
1986	3.3613214418227533
1987	3.5751254080738915
1988	3.5618183472642895
1989	3.2937696617243404
1990	3.084592221463094
1991	3.038116319233295
1992	3.1384986804577575
1993	3.283448481648955
1994	3.5775257440492374
1995	3.3820782748960014
1996	3.3679248109787165
1997	3.341259621981823
1998	2.9128492124385077
1999	3.1360919749988594
2000	2.9946514701891678
2001	3.1389665717048696
2002	3.094656501821154
2003	3.151835586065748
2004	3.322423319344751
2005	3.3466929152385494
2006	3.178573887499139
2007	3.111614177597266
2008	3.4002044917674428
2009	3.5157322695804245
2010	3.2235981482611145
2011	3.0694254445964426
2012	3.1432323895638117
2013	3.053439884035514
2014	3.311013963440504