Year	% of total fuel combustion
1971	0
1972	0
1973	6.557377049180328
1974	7.142857142857142
1975	5.263157894736842
1976	6.837606837606838
1977	32.57575757575758
1978	31.60919540229885
1979	19.548872180451127
1980	18.6046511627907
1981	27.77777777777778
1982	26.704545454545453
1983	23.626373626373624
1984	15.894039735099339
1985	19.04761904761905
1986	31.756756756756754
1987	24.21875
1988	23.611111111111114
1989	36.283185840707965
1990	35.16483516483516
1991	36.44859813084112
1992	33.33333333333333
1993	32.5
1994	26.724137931034488
1995	25.954198473282442
1996	24.822695035460992
1997	25
1998	25.30864197530864
1999	25.657894736842106
2000	21.917808219178085
2001	24.324324324324323
2002	28.260869565217394
2003	25.179856115107913
2004	25.874125874125873
2005	21.38728323699422
2006	20.555555555555554
2007	21.649484536082475
2008	21.5
2009	19.41747572815534
2010	23.684210526315788
2011	24.080267558528426
2012	23.65930599369085
2013	24.7787610619469
2014	23.782234957020055