Year	% of total fuel combustion
1971	2.1430963277151465
1972	2.071583514099783
1973	1.9515265974189486
1974	1.598561294834649
1975	2.1527371907266706
1976	1.9251725390483105
1977	2.0333996711949465
1978	1.874274340686681
1979	2.1401819154628146
1980	2.339054239988414
1981	2.4003368893879844
1982	2.287886872998933
1983	2.2062531517902166
1984	2.053162236480293
1985	2.0426500539115846
1986	2.096473839130174
1987	2.178423236514523
1988	2.2223539172691718
1989	3.6006938214008017
1990	3.09053448066901
1991	3.15867707172055
1992	3.6542132533406053
1993	4.076703505818633
1994	4.450858271304877
1995	4.7854657904909175
1996	5.79604409857328
1997	6.195766766685589
1998	6.1145764937623115
1999	5.70803033857221
2000	5.6954525255517705
2001	5.507696653015111
2002	5.812389380530974
2003	5.244492941417173
2004	6.155458057756531
2005	6.78136455007686
2006	6.676498950592775
2007	7.0021362449560876
2008	6.606540142754385
2009	6.556648330277269
2010	6.362751274268369
2011	7.010129469376803
2012	6.652533079903501
2013	7.655038759689921
2014	6.995105005526606