Year	% of total fuel combustion
1971	9.034184060488904
1972	8.750402132450938
1973	8.850682504949463
1974	8.62406744107811
1975	8.936550491510276
1976	8.884530165994697
1977	8.751367401156429
1978	8.390800858760004
1979	8.098961906068505
1980	8.227903707608505
1981	8.671747730975099
1982	8.835318204100464
1983	9.11994583376264
1984	9.169258494898699
1985	9.261166909892124
1986	9.101403069988594
1987	9.277543328821297
1988	9.506415172826184
1989	9.311040645719226
1990	9.5004934335383
1991	9.12529493322955
1992	9.407211919667688
1993	9.26389239562054
1994	8.94707654165262
1995	9.026657611002632
1996	8.637548566234855
1997	8.116770209686363
1998	7.898181161709618
1999	8.174643003786668
2000	8.15410068541716
2001	8.01251056341096
2002	7.960047636847275
2003	7.457468127744851
2004	7.325372263719883
2005	7.116918564067168
2006	7.0976675158163705
2007	7.420970474436085
2008	6.83284560871558
2009	6.88765555218315
2010	6.690525088621838
2011	6.507813322108807
2012	6.358447200262672
2013	6.469268786434154
2014	6.376699315662295