Year	% of total fuel combustion
1971	3.9666316778078565
1972	3.9895877603059913
1973	4.440780726479818
1974	3.859769888877964
1975	3.306774743241375
1976	3.4384694932781796
1977	3.582001184132624
1978	3.8097728956889396
1979	5.132324003052086
1980	4.434775971299901
1981	5.542829376648619
1982	5.62477634275676
1983	6.063375990249849
1984	7.401535380507346
1985	5.832734626540009
1986	4.16869700808888
1987	3.9990957386684753
1988	4.992076069730587
1989	4.365846368436783
1990	5.414679210422126
1991	5.884820414227039
1992	5.6539475230405065
1993	5.298471440064362
1994	5.78455724364933
1995	5.754013113271536
1996	5.849627309063413
1997	6.052729298180467
1998	4.501486220968311
1999	4.880754946158698
2000	4.4921611787430935
2001	4.530390402333135
2002	4.621830775150712
2003	4.985008282137839
2004	4.914078987036477
2005	4.579558717278942
2006	4.209538375973303
2007	3.4907256597985423
2008	4.278058968241581
2009	5.439933380478101
2010	4.320499793007414
2011	2.82344788032309
2012	3.4315039424601848
2013	2.9657860358658223
2014	3.0183148732218634