Year	% of total fuel combustion
1971	26.61290322580645
1972	28.019323671497588
1973	26.71394799054373
1974	28.870292887029287
1975	27.272727272727277
1976	24.756335282651072
1977	26.306620209059233
1978	25.079872204472846
1979	28.278688524590162
1980	26.01010101010101
1981	25.307125307125304
1982	22.320302648171502
1983	24.67105263157895
1984	25
1985	25.672877846790893
1986	25.201612903225808
1987	21.865596790371114
1988	22.96296296296296
1989	27.101200686106345
1990	27.809680065627568
1991	24.58100558659218
1992	25.677710843373497
1993	22.554744525547445
1994	21.029731689630168
1995	20.883820384889525
1996	21.25930941096818
1997	20.428015564202333
1998	20.509633312616533
1999	19.59739490822972
2000	20.53318207600681
2001	20.10810810810811
2002	19.762419006479483
2003	23.949809056192034
2004	24.317226890756302
2005	23.47200821777093
2006	24.851190476190474
2007	23.938960419647117
2008	23.895486935866984
2009	20.91812588736394
2010	19.836839845427225
2011	19.064748201438853
2012	19.855134213890075
2013	20.29598308668076
2014	21.311475409836063