Year	% of total fuel combustion
1971	29.977628635346765
1972	29.3550577053632
1973	30.443523055660265
1974	31.25148703307161
1975	30.668027673811952
1976	30.906200317965027
1977	28.954209158168368
1978	27.634194831013914
1979	28.621621621621625
1980	25.72403462050599
1981	26.04547622833519
1982	25.631313131313128
1983	24.17699115044248
1984	23.338870431893685
1985	23.564934634016858
1986	22.702875399361023
1987	21.83152333431171
1988	21.56577252618021
1989	20.174914444021944
1990	14.224137931034484
1991	13.250086715227193
1992	13.027737226277372
1993	13.074653290056062
1994	13.280063194993012
1995	17.501566369305127
1996	16.015502550511528
1997	14.667576791808871
1998	16.248009451892948
1999	16.341025830076923
2000	16.1818486029113
2001	15.647115406637198
2002	15.972946002882802
2003	18.306501006212265
2004	17.541210519692967
2005	17.639460724953583
2006	18.16708643276909
2007	18.827851122547923
2008	17.91094373061586
2009	17.102543869537445
2010	17.224219970215398
2011	17.886691908568228
2012	17.52993547051313
2013	16.76237589511191
2014	16.86850772738789