Year	% of total fuel combustion
1971	7.925393086765549
1972	7.742371216307483
1973	6.949114548307554
1974	6.815974096060443
1975	6.572399862048578
1976	6.4292961903883405
1977	5.527938875080549
1978	6.764252696456087
1979	6.058166448626345
1980	4.856512141280353
1981	3.9238025794102898
1982	3.643012544553997
1983	3.577267044908164
1984	4.3432876463647085
1985	4.292827344906472
1986	3.590795169742538
1987	3.468109582037408
1988	3.855380397532557
1989	4.408225309293585
1990	4.642769256008531
1991	4.948047595106419
1992	4.983431047667602
1993	6.140350877192983
1994	5.6339163375513825
1995	4.743022136669875
1996	4.054455078269902
1997	3.964509541581579
1998	3.6681850875089905
1999	3.518559031575877
2000	3.2761755374139967
2001	4.04777704047777
2002	4.8252860902025585
2003	5.048097631012204
2004	5.300588658338438
2005	5.780439979585807
2006	6.463258102470852
2007	7.648681790312691
2008	7.653410836227878
2009	7.821340944369336
2010	3.412499385356739
2011	4.123685210999873
2012	5.553238980598003
2013	5.59151469337617
2014	5.469053661659465