Year	% of total fuel combustion
1971	3.278688524590164
1972	3.2
1973	2.8985507246376816
1974	2.72108843537415
1975	3.1055900621118013
1976	3.571428571428571
1977	3.296703296703297
1978	3.4090909090909087
1979	3.5897435897435903
1980	3.431372549019608
1981	3.5000000000000004
1982	3.6269430051813476
1983	3.664921465968587
1984	3.431372549019608
1985	3.7735849056603774
1986	3.9215686274509802
1987	4.3478260869565215
1988	5.583756345177665
1989	5.769230769230769
1990	6.103286384976527
1991	6.572769953051644
1992	6.896551724137932
1993	7.52212389380531
1994	7.725321888412016
1995	8.06451612903226
1996	8.846153846153847
1997	9.059233449477352
1998	9.404388714733543
1999	10.140845070422536
2000	9.943181818181818
2001	9.39947780678851
2002	9.693877551020408
2003	10.761154855643046
2004	9.684684684684685
2005	9.523809523809524
2006	9.684684684684685
2007	7.429718875502007
2008	7.088122605363985
2009	7.076350093109869
2010	6.227106227106228
2011	5.526770293609672
2012	5.291005291005291
2013	5
2014	4.936305732484076