Year	% of total fuel combustion
1971	4.310344827586206
1972	3.50109409190372
1973	3.6717062634989204
1974	3
1975	3.26295585412668
1976	3.364485981308411
1977	3.169014084507042
1978	3.602058319039451
1979	3.7398373983739837
1980	3.6334913112164293
1981	5.833333333333333
1982	5.181347150259067
1983	4.296296296296296
1984	4.23728813559322
1985	6.420545746388442
1986	5.091937765205092
1987	4.9504950495049505
1988	5.1660516605166045
1989	9.688581314878892
1990	12.7027027027027
1991	12.093628088426527
1992	13.953488372093023
1993	16.276477146042364
1994	13.881019830028329
1995	14.2602495543672
1996	14.80865224625624
1997	14.296134208606857
1998	7.6335877862595405
1999	7.369682444577591
2000	7.166301969365427
2001	7.122826696578801
2002	5.94059405940594
2003	5.8229352346999415
2004	7.207207207207208
2005	6.986143187066975
2006	7.733910221741482
2007	8.144552319309602
2008	8.44017094017094
2009	8.596300326441785
2010	7.824726134585289
2011	7.11340206185567
2012	7.021063189568705
2013	7.262569832402234
2014	7.580477673935617