Year	% of total fuel combustion
1971	23.731603408210695
1972	24.388975559022363
1973	24.43793540215326
1974	24.820691154096934
1975	24.71275687742105
1976	25.240398624628476
1977	25.993462049238943
1978	27.41556406685237
1979	25.28633421071353
1980	24.31329220759292
1981	25.7295095687106
1982	26.22996551024549
1983	27.798568554989004
1984	29.30822853702031
1985	29.534738902232895
1986	27.363905885321387
1987	27.331208804259614
1988	27.07752888294513
1989	26.87439315032218
1990	27.618602813055737
1991	27.955052942447594
1992	27.590272660280032
1993	26.628340867032733
1994	26.213606143970658
1995	25.101242941019862
1996	25.017185836175173
1997	24.206029443740967
1998	24.815098189237442
1999	24.976360083212505
2000	25.332192408776972
2001	24.482727085667253
2002	24.669976058163286
2003	24.474904382384995
2004	24.458026063238712
2005	24.357310766337566
2006	24.58605117912694
2007	25.168746076922414
2008	24.956660039761434
2009	25.09289600944474
2010	24.95702498280999
2011	24.78846407887144
2012	25.064567382193133
2013	24.980393936055062
2014	24.74428848738241