Year	% of total fuel combustion
1971	6.102490546355458
1972	5.809786759090642
1973	5.699563594300438
1974	5.411742188621466
1975	5.145834223000384
1976	5.090729633285247
1977	4.916272358132823
1978	4.68590321611061
1979	4.524783415055514
1980	4.30227425836876
1981	3.990303134318751
1982	3.8844563508240633
1983	4.121231277107588
1984	4.426153924967127
1985	3.848276309809777
1986	4.015374679037822
1987	4.063095396340113
1988	4.338816940847043
1989	4.123982829905459
1990	2.8098191896528966
1991	3.0334997169762774
1992	2.9425254913029684
1993	2.4944035817077075
1994	2.2193759926225725
1995	2.294590679786224
1996	2.155384126433793
1997	2.0320884997893742
1998	2.1681476418318533
1999	2.165634158754673
2000	2.100381656779696
2001	2.509923323396725
2002	1.8767207096971557
2003	1.7943168848109337
2004	1.8741745456070098
2005	2.0929018789144043
2006	2.219501941291392
2007	2.2856536627629414
2008	1.7586513853343717
2009	1.833630770050342
2010	1.7122585407866133
2011	1.613902236785582
2012	1.4759691690664236
2013	1.4250446204799812
2014	1.3269825805345827