Year	% of total fuel combustion
1971	13.392857142857142
1972	12.931034482758621
1973	12.598425196850393
1974	12.8
1975	12.030075187969924
1976	12.676056338028168
1977	13.924050632911394
1978	15.822784810126581
1979	15.476190476190476
1980	15.294117647058824
1981	14.285714285714285
1982	13.20754716981132
1983	11.931818181818182
1984	10.21505376344086
1985	10.778443113772456
1986	15.882352941176473
1987	15.263157894736842
1988	15.311004784688997
1989	14.655172413793101
1990	15.13761467889908
1991	15.277777777777777
1992	15.853658536585366
1993	13.076923076923075
1994	11.666666666666666
1995	10.364145658263306
1996	9.943181818181818
1997	10.497237569060774
1998	8.796296296296296
1999	9.174311926605505
2000	6.45879732739421
2001	7.183364839319471
2002	9.608540925266905
2003	11.057692307692308
2004	5.689900426742532
2005	5.865921787709497
2006	5.9375
2007	3.448275862068966
2008	3.426395939086295
2009	3.5135135135135136
2010	3.6784741144414173
2011	3.1026252983293556
2012	3.7125748502994016
2013	3.6686390532544384
2014	4.914285714285714