Year	% of total fuel combustion
1971	3.205629397967162
1972	4.1302621127879275
1973	4.224270353302612
1974	5.581089954038084
1975	6.415792720542875
1976	5.7223796033994345
1977	6.514285714285715
1978	6.4300411522633745
1979	6.117755289788409
1980	5.656395103419165
1981	5.5226824457593695
1982	5.421686746987952
1983	5.127334465195246
1984	5.063291139240507
1985	4.437689969604863
1986	4.948963810702135
1987	4.980729321079159
1988	5.243970835670219
1989	4.5889101338432114
1990	4.133897963299052
1991	3.3539128983814455
1992	3.418124006359301
1993	3.6905816356657817
1994	3.5082910785254215
1995	3.4686439612919444
1996	4.334910331169545
1997	3.0841986223912823
1998	3.183539768655953
1999	3.668171557562077
2000	3.4599669651395284
2001	3.2389336433851015
2002	3.392108800506049
2003	2.794516420608617
2004	2.7364542104544833
2005	2.7661895898851165
2006	2.7693639117265256
2007	3.3535557802494105
2008	2.8328165238871077
2009	2.915709489309065
2010	2.9289364167939738
2011	2.653295727567116
2012	2.270018139414356
2013	2.162265595101416
2014	1.8909849446762197