Year	% of total fuel combustion
1971	16.190476190476186
1972	16.796875
1973	18.439306358381504
1974	17.968323320589842
1975	18.57688634192932
1976	17.594473791141812
1977	16.099614170466502
1978	15.975975975975974
1979	16.962940644772523
1980	18.271803103263775
1981	19.200588523786173
1982	20.184518451845186
1983	22.825131810193323
1984	23.91863455693243
1985	24.893569347972214
1986	25.372093023255818
1987	26.113776559287185
1988	24.46738414232374
1989	24.03992189195053
1990	25.308947108255072
1991	26.06181899043807
1992	26.159769008662177
1993	28.84970268607751
1994	29.958866544789764
1995	28.720905402519755
1996	28.108931632070078
1997	27.136788445199663
1998	29.46058091286308
1999	29.156626506024093
2000	28.6618444846293
2001	27.484578478409865
2002	28.833311509755138
2003	24.83468972533062
2004	26.571141277023624
2005	29.35018050541516
2006	31.55773832011082
2007	33.39651250947688
2008	30.815109343936385
2009	30.430455337148548
2010	31.754349193041296
2011	32.27048371174729
2012	33.24749379196174
2013	32.70622286541244
2014	33.60485111774821