Year	% of total fuel combustion
1971	13.753581661891115
1972	11.363636363636365
1973	10.579345088161208
1974	13.575525812619501
1975	12.647554806070826
1976	12.536443148688045
1977	11.495673671199013
1978	11.688311688311689
1979	13.608247422680414
1980	12.980769230769232
1981	12.711864406779661
1982	11.675126903553299
1983	13.615870153291254
1984	12.701252236135957
1985	15.608919382504288
1986	15.197313182199832
1987	16.867469879518072
1988	12.8559804719284
1989	13.477537437603996
1990	18.093093093093092
1991	18.188353702372392
1992	18.690958164642375
1993	17.73504273504274
1994	18.657718120805367
1995	16.057519472738164
1996	15.729166666666666
1997	14.977973568281937
1998	15.686274509803924
1999	17.070217917675546
2000	17.926089354660785
2001	16.07883817427386
2002	16.717171717171716
2003	16.130678917815214
2004	16.434038721296712
2005	16.722408026755854
2006	15.342250196695515
2007	14.258336527405138
2008	15.066921606118546
2009	14.702815432742442
2010	13.104524180967239
2011	14.037758830694274
2012	13.74670956420006
2013	13.576805129634796
2014	13.271365866253552