Year	% of total fuel combustion
1971	8.738935561611747
1972	8.51294939512694
1973	8.602919849173354
1974	8.432780847145487
1975	8.761450346925024
1976	8.713070458071224
1977	8.561894685439897
1978	8.236337773971032
1979	7.985666383640104
1980	8.11555666348138
1981	8.547656110093259
1982	8.713664579288467
1983	8.958854601056435
1984	8.999424168471853
1985	9.15022906159514
1986	9.001869941024937
1987	9.135325531189638
1988	9.344570214027977
1989	9.15975004770082
1990	9.381724980051745
1991	9.094218641738987
1992	9.357021217839554
1993	9.191863784437306
1994	8.85944456222175
1995	8.92607945089364
1996	8.53569587754189
1997	7.9799565542797675
1998	7.764212300211528
1999	8.034709234819141
2000	8.034407650682368
2001	7.892573540005256
2002	7.839700602858498
2003	7.376578883908896
2004	7.299246978421818
2005	7.066453297397457
2006	7.007739891820816
2007	7.30341948252698
2008	6.740922100762095
2009	6.77429811703687
2010	6.580139246113871
2011	6.41426964486582
2012	6.268300819135399
2013	6.382470997111949
2014	6.291739682883795