Year	% of total fuel combustion
1971	4.509803921568627
1972	3.2315978456014367
1973	4.0229885057471275
1974	3.9761431411530825
1975	4.315196998123827
1976	4.212454212454212
1977	5.018587360594796
1978	6.043956043956046
1979	5.04201680672269
1980	10.674157303370784
1981	11.27348643006263
1982	10.762331838565025
1983	12.849162011173188
1984	14.018691588785048
1985	15.614617940199341
1986	14.527027027027026
1987	12.048192771084336
1988	10.07025761124122
1989	9.523809523809526
1990	11.666666666666666
1991	11.138014527845039
1992	10.864745011086477
1993	11.792452830188681
1994	13.74045801526718
1995	12.528473804100226
1996	11.890838206627679
1997	11.17533718689788
1998	11.214953271028037
1999	9.21875
2000	11.001964636542239
2001	11.894273127753301
2002	12.530120481927712
2003	13.022113022113025
2004	10.576923076923077
2005	10.679611650485437
2006	9.375000000000004
2007	10.053859964093355
2008	7.764390896921018
2009	7.248322147651007
2010	8.557046979865774
2011	7.063711911357343
2012	5.990220048899755
2013	7.1729957805907185
2014	7.974481658692185