Year	% of total fuel combustion
1971	19.94233541566555
1972	19.970341077607515
1973	20.322580645161292
1974	18.34394904458599
1975	18.899917287014063
1976	18.225228810187026
1977	17.37072104879825
1978	16.902356902356903
1979	17.82345013477089
1980	17.38845144356955
1981	18.274613105037865
1982	17.371353654539494
1983	16.08918348900271
1984	16.344210222350565
1985	16.972334473111594
1986	17.190839694656486
1987	16.1607400982943
1988	16.050397151465354
1989	15.050344462109166
1990	14.868035190615835
1991	14.01129943502825
1992	12.246820536975978
1993	9.933774834437086
1994	8.940397350993377
1995	8.778966131907309
1996	9.016393442622952
1997	10.420613868889731
1998	9.558541266794625
1999	8.739308293045742
2000	7.937088514996342
2001	8.352229780801208
2002	8.161648177496039
2003	7.7142857142857135
2004	8.133773740710156
2005	7.624750499001995
2006	7.193396226415095
2007	7.031546940326873
2008	7.145661562622693
2009	4.807364473235595
2010	3.824969400244798
2011	4.098085320792745
2012	4.161205766710354
2013	4.214819850441876
2014	4.278438030560272