Year	% of total fuel combustion
1971	7.964601769911505
1972	8.032128514056225
1973	7.984790874524716
1974	7.380073800738007
1975	7.641196013289036
1976	7.586206896551724
1977	7.18562874251497
1978	6.933333333333333
1979	6.650831353919242
1980	8.076009501187649
1981	10.46831955922865
1982	11.28526645768025
1983	13.09090909090909
1984	11.97411003236246
1985	11.635220125786162
1986	15.948275862068966
1987	12.5
1988	12.413793103448276
1989	14.473684210526317
1990	14.641744548286603
1991	14.076246334310849
1992	12.559241706161139
1993	11.663066954643629
1994	11.382113821138212
1995	10.921501706484642
1996	11.713286713286715
1997	11.833333333333334
1998	9.81675392670157
1999	11.451398135818907
2000	10.256410256410255
2001	10.122358175750833
2002	9.326424870466319
2003	6.639004149377594
2004	6.73828125
2005	5.273069679849342
2006	5.4562558795860765
2007	5.231037489102005
2008	5.951219512195122
2009	4.986642920747997
2010	5.813953488372093
2011	6.202290076335878
2012	7.1765816808309735
2013	6.546644844517186
2014	4.770755885997521