Year	% of total fuel combustion
1971	7.340018608497881
1972	6.895376299578777
1973	7.33233636259059
1974	6.381738078783691
1975	6.4495568170500945
1976	5.618565369308097
1977	5.750888184952485
1978	5.866412148688493
1979	6.401655276192867
1980	4.721249379969638
1981	5.3202537330189745
1982	5.398891930477151
1983	5.53489389630278
1984	5.943438679082005
1985	5.040566200586915
1986	4.244181861187382
1987	3.8980207983898034
1988	4.199540002382458
1989	3.9609609350011663
1990	7.525442145192429
1991	7.4935131347184605
1992	6.805867392318158
1993	6.65579926353938
1994	6.748583247358409
1995	4.126674081066178
1996	4.0348258476554015
1997	4.002798726402353
1998	3.655031338186354
1999	3.775463601091165
2000	3.7492769627175684
2001	3.840262582056893
2002	3.5486165768602054
2003	3.48106553149449
2004	3.6585239067227144
2005	3.701243649908879
2006	3.52067511620228
2007	3.26351202753226
2008	3.3513719336302588
2009	3.9600313371909226
2010	3.555617664973013
2011	2.835143528982958
2012	3.157233528083566
2013	2.952946768060838
2014	2.8156125874972813