Year	% of total fuel combustion
1971	15.2332361516035
1972	14.216366158113733
1973	13.90048154093098
1974	13.930506853681862
1975	14.792332268370608
1976	15.238095238095239
1977	17.026946994373702
1978	17.626321974148063
1979	16.767554479418887
1980	15.095986038394415
1981	15.276967930029155
1982	16.35710005991612
1983	17.080207732256202
1984	18.53949329359165
1985	16.950646298472385
1986	17.084548104956266
1987	17.624854819976772
1988	16.31030701754386
1989	15.317997293640056
1990	14.752342704149932
1991	15.955313663706676
1992	16.937090805579277
1993	18.925166136954637
1994	18.95302013422819
1995	20.77922077922078
1996	19.94362226920366
1997	21.119094273895055
1998	23.75556454876568
1999	21.08108108108108
2000	21.828742739366685
2001	22.020130672788277
2002	23.270134500081028
2003	22.388294524858402
2004	22.759830434147055
2005	24.81276005547851
2006	24.770404863536417
2007	25.574780753733112
2008	24.971597364235404
2009	23.208486685429747
2010	22.60042931616069
2011	22.693122712386824
2012	22.182849043231744
2013	22.23991952384944
2014	22.935634549916877