Year	% of total fuel combustion
1971	24.819536545378913
1972	24.4933131118158
1973	24.84734812962384
1974	25.55161973363941
1975	25.888798228231728
1976	26.63906142167011
1977	26.42774044555573
1978	26.475180534773273
1979	26.40356092132742
1980	25.65747086042289
1981	24.00948336048406
1982	23.633899478070305
1983	23.962672397297577
1984	23.644740284277535
1985	24.076458637365153
1986	22.24711072022427
1987	23.66563155240598
1988	22.462854394425886
1989	22.72049331344705
1990	22.0501530909183
1991	21.770329108997593
1992	21.041669132179077
1993	20.89540248353111
1994	21.094353163772386
1995	21.075643093641226
1996	21.740693760549735
1997	21.900993449063414
1998	21.12199304960058
1999	20.812993293489665
2000	20.977441634496703
2001	20.423756131134404
2002	21.03844849917853
2003	20.619110561548624
2004	20.882414893789395
2005	20.535847339979135
2006	20.75750273487404
2007	19.726864490164306
2008	20.552832916123112
2009	18.76020754744251
2010	20.532476599090398
2011	20.800668210038932
2012	19.031141868512112
2013	18.985435710313716
2014	18.27667410645663