Year	% of total fuel combustion
1971	13.333333333333334
1972	12.426900584795323
1973	11.177170035671818
1974	11.521739130434785
1975	11.285846438482887
1976	11.524434719183075
1977	11.778703152885187
1978	11.92570869990225
1979	10.631229235880399
1980	10.295857988165679
1981	10.907165548888106
1982	10.465479537644487
1983	11.924939467312349
1984	13.517060367454068
1985	13.278791692888609
1986	16.24298448332783
1987	17.292268206608917
1988	15.716911764705882
1989	14.906457453228727
1990	15.039201710620102
1991	12.534225737754792
1992	12.74930573087604
1993	12.085176991150444
1994	11.807149885208265
1995	11.687519072322242
1996	11.370502609173304
1997	10.63572637176698
1998	7.322897320244097
1999	10.169921379660158
2000	9.209323583180987
2001	10.68609593199757
2002	9.753231492361927
2003	6.641998149861239
2004	3.9941100681023376
2005	6.382978723404256
2006	4.803149606299213
2007	2.7742749054224465
2008	4.814253222137983
2009	4.263565891472869
2010	3.1737493275954813
2011	3.869586695208299
2012	2.4652338811630847
2013	2.5562206762659767
2014	2.609707446808511