Year	% of total fuel combustion
1971	6.299212598425196
1972	6.338028169014084
1973	5.521472392638037
1974	5.063291139240507
1975	4.597701149425287
1976	5.555555555555556
1977	4.385964912280702
1978	4.508196721311475
1979	4.938271604938271
1980	5.092592592592593
1981	3.9603960396039604
1982	2.9761904761904763
1983	3.4682080924855487
1984	3.804347826086957
1985	3.0769230769230766
1986	3.398058252427185
1987	3.181818181818182
1988	2.5974025974025974
1989	3.8022813688212933
1990	5
1991	3.985507246376812
1992	2.849740932642487
1993	2.8871391076115485
1994	3.146067415730337
1995	2.9279279279279278
1996	4.076738609112709
1997	4.645476772616137
1998	4.615384615384617
1999	5.482456140350878
2000	4.444444444444445
2001	4.0733197556008145
2002	4.780876494023905
2003	3.7593984962406015
2004	4.708097928436912
2005	3.8602941176470584
2006	3.8525963149078724
2007	3.598200899550225
2008	3.592814371257485
2009	3.7735849056603774
2010	3.7821482602118
2011	3.8461538461538463
2012	3.947368421052632
2013	3.9270687237026656
2014	3.9051603905160395