Year	% of total fuel combustion
1971	6.458848712460104
1972	6.577095637321527
1973	6.710718170666789
1974	6.761937166836794
1975	6.5044836732116345
1976	6.390366844021283
1977	6.2850405646065575
1978	6.027934508448877
1979	6.032346326299656
1980	5.789705235371753
1981	6.4462151981778115
1982	6.37889925782328
1983	6.295792479258699
1984	6.347872820158017
1985	5.99191727820187
1986	6.071491253729599
1987	5.810840345317453
1988	5.708158423069904
1989	5.377697665533558
1990	6.0955518945634255
1991	5.94883752829024
1992	5.472985707210384
1993	5.247385358004829
1994	5.471288017078681
1995	4.775066849550411
1996	3.103315007538064
1997	4.074176013211312
1998	4.238771339705102
1999	4.581097670312693
2000	2.605469509429071
2001	2.651185740278164
2002	2.72982014697052
2003	2.7384753566828373
2004	2.669012027382298
2005	2.6274288039208002
2006	2.470538891369349
2007	2.2805658746832767
2008	2.233493935065249
2009	2.1772762271551813
2010	2.03787441368617
2011	1.9496751329001767
2012	2.018450359994293
2013	2.0788812260365725
2014	2.074621215455994