Year	% of total fuel combustion
1971	2.5570644322450162
1972	2.613556953179595
1973	2.744990392533626
1974	3.2797681770284512
1975	3.561887800534283
1976	3.1685977772523057
1977	3.217517595799352
1978	4.333614508646141
1979	4.819514114291335
1980	5.133660160947183
1981	4.779444793819064
1982	4.324324324324325
1983	4.151877837391663
1984	3.3041241257335803
1985	3.546318473306034
1986	2.8173447705988828
1987	3.166899728551452
1988	3.289580294927888
1989	3.7662020053802885
1990	4.014379868184542
1991	3.76285868976719
1992	3.4673212641914706
1993	3.463637376099788
1994	2.553451435552841
1995	3.3063251437532672
1996	3.039332538736591
1997	1.747062461348175
1998	3.5546613011401744
1999	1.370073891625616
2000	2.444253859348199
2001	2.1712073018946203
2002	2.2730563196756917
2003	2.1692896639727772
2004	2.1500901650714384
2005	1.7257400769945574
2006	1.3066771200836274
2007	1.88082819661767
2008	1.7334470019892017
2009	1.8886822149091431
2010	2.013729977116705
2011	2.8856584942503796
2012	2.787234042553192
2013	4.329524954900782
2014	3.544973544973545