Year	% of total fuel combustion
1971	18.82883168149626
1972	18.744845540088036
1973	18.279723340088093
1974	17.987515140221742
1975	18.328331575959115
1976	17.941394514027085
1977	18.036138816304746
1978	17.216655148583275
1979	17.246224517368717
1980	16.47901491922289
1981	17.05334318702221
1982	16.931679189236412
1983	16.873092503190726
1984	16.648198446607946
1985	17.63569517702449
1986	17.18435203571377
1987	16.813621161447248
1988	16.80345006737093
1989	16.247080831917057
1990	15.880094728643558
1991	15.06068166044531
1992	13.6722065893895
1993	13.002948476620412
1994	11.6221027032382
1995	11.2239284895714
1996	9.64152501352467
1997	10.49657090466251
1998	8.771523917883837
1999	9.29725180103106
2000	8.637359465806082
2001	8.330046383439765
2002	7.919928140639036
2003	7.432167294785118
2004	7.2949074832159795
2005	6.712676316384253
2006	6.36712576202303
2007	6.0788561989853385
2008	5.712930297899554
2009	5.501477749247454
2010	5.324789649313161
2011	5.1552064598085705
2012	5.227733802524506
2013	5.224399425644915
2014	5.237496083203904