Year	% of total fuel combustion
1971	50
1972	46.15384615384615
1973	34.48275862068966
1974	33.33333333333333
1975	38.88888888888889
1976	43.74999999999999
1977	21.37404580152672
1978	30.32258064516129
1979	30.687830687830687
1980	28.888888888888893
1981	23.50597609561753
1982	21.08843537414966
1983	19.02313624678663
1984	19.477911646586342
1985	19.715808170515096
1986	14.606741573033707
1987	13.946117274167987
1988	17.194570135746606
1989	16.520467836257307
1990	4.724409448818897
1991	3.687943262411348
1992	4.419475655430712
1993	5.405405405405405
1994	6
1995	5.105513955071477
1996	6.296048225050235
1997	9.946595460614152
1998	10.543549443352978
1999	6.807780320366132
2000	5.634492895639392
2001	7.257714037375053
2002	6.769355492501012
2003	6.991358994501177
2004	3.3333333333333335
2005	3.6901865369018654
2006	2.898550724637681
2007	3.0502885408079146
2008	3.369839932603201
2009	3.428571428571429
2010	3.139754485363551
2011	2.769230769230769
2012	2.66887539112829
2013	2.6381019830028327
2014	2.5542570951585977