Year	% of total fuel combustion
1971	5.1575931232091685
1972	5.6818181818181825
1973	5.037783375314862
1974	13.001912045889103
1975	13.322091062394605
1976	14.43148688046647
1977	12.608158220024723
1978	11.363636363636363
1979	9.278350515463918
1980	8.557692307692308
1981	7.796610169491524
1982	8.460236886632826
1983	8.115419296663662
1984	8.318425760286226
1985	9.090909090909092
1986	10.831234256926953
1987	10.327022375215149
1988	11.228641171684298
1989	13.061564059900169
1990	9.534534534534535
1991	9.345794392523365
1992	9.176788124156547
1993	9.686609686609687
1994	9.798657718120806
1995	9.886159376872378
1996	9.375
1997	9.446891825746452
1998	9.607843137254903
1999	11.2590799031477
2000	10.64533921676779
2001	10.58091286307054
2002	10.707070707070706
2003	11.3323124042879
2004	10.625844214317874
2005	10.326086956521738
2006	10.14948859166011
2007	10.272134917592947
2008	10.783938814531549
2009	10.114702815432741
2010	9.422776911076443
2011	9.59196102314251
2012	9.827434922491957
2013	9.590186785614721
2014	9.19184095016783