Year	% of total fuel combustion
1971	4.612500616644469
1972	4.436115196659865
1973	4.869548836771216
1974	4.136029411764707
1975	3.640379581151832
1976	3.721307674472525
1977	3.830028328611899
1978	4.06936416184971
1979	5.160603371783496
1980	4.497559333445548
1981	5.348515156177874
1982	5.368067323433955
1983	5.790724042978242
1984	6.952772684473961
1985	5.591585501025872
1986	4.139768640873445
1987	3.9450602025356836
1988	4.830161634069519
1989	4.305548242149789
1990	5.15813065493484
1991	5.5862197277434955
1992	5.364657934761742
1993	5.009571533134397
1994	5.438610533055866
1995	5.384966505878434
1996	5.455336563337882
1997	5.618077785337453
1998	4.273991838167537
1999	4.599148832437813
2000	4.244044820561041
2001	4.30914383989393
2002	4.377145089431045
2003	4.65702558315207
2004	4.57052399356691
2005	4.286035637964554
2006	3.9525065963060686
2007	3.296620242814838
2008	3.9970001304291123
2009	5.036076557265678
2010	4.066986980954135
2011	2.7639835853545596
2012	3.3025178204181063
2013	2.8705586213573446
2014	2.915648248916166