Year	% of total fuel combustion
1971	26.592060374237573
1972	26.274013294051763
1973	25.62061428735764
1974	25.583102971665515
1975	25.09909371576536
1976	24.647321511986394
1977	24.804424298640157
1978	25.759719121231235
1979	24.913787698288292
1980	25.27619534338409
1981	24.24216908049848
1982	22.280579968303453
1983	21.880697148691024
1984	21.235302941142535
1985	21.534610737096497
1986	20.746819691687488
1987	20.301912110030187
1988	20.251807460758172
1989	20.264698000501387
1990	15.157600628656247
1991	16.10778613231312
1992	15.763208123194087
1993	16.27005496771314
1994	16.935022516465622
1995	17.403900971037114
1996	18.519254497645466
1997	18.882103650300902
1998	18.90192041801695
1999	18.464633830227573
2000	18.57123788027716
2001	18.59643638637074
2002	18.82908518496095
2003	18.745596001714382
2004	18.885219313901143
2005	18.603013331019156
2006	17.92944045109344
2007	18.29153763396121
2008	19.010338541065703
2009	19.37270640625644
2010	19.554974305158215
2011	19.61693543283968
2012	19.853367384307937
2013	19.73288973384031
2014	19.429162246479358