Year	% of total fuel combustion
1971	7.106413994169096
1972	7.177531206657421
1973	6.934189406099518
1974	7.459356072680905
1975	6.964856230031949
1976	6.912442396313363
1977	7.906425821735267
1978	7.344300822561692
1979	8.504842615012107
1980	8.08609656777196
1981	8.250728862973762
1982	6.560814859197125
1983	9.290248124639353
1984	9.150521609538004
1985	9.136310223266745
1986	7.6967930029154505
1987	8.768873403019745
1988	8.63486842105263
1989	8.606224627875507
1990	6.024096385542168
1991	5.814952735605843
1992	4.953031596925705
1993	4.709621496677261
1994	3.838926174496644
1995	4.214653271257045
1996	3.7585153864223626
1997	3.3311561071195293
1998	3.5410764872521243
1999	7.7027027027027035
2000	6.745362563237774
2001	7.0280769909941725
2002	5.785123966942148
2003	5.805538074260541
2004	6.4464259611167956
2005	5.561719833564494
2006	5.924201267623854
2007	4.918227068025599
2008	4.7375596455351054
2009	3.7670491448365455
2010	4.231830726770928
2011	3.5445964168753616
2012	4.544649184975194
2013	4.149551513119289
2014	4.26727891695036