Year	% of total fuel combustion
1971	3.7594744820616466
1972	3.6850515713524774
1973	3.513334802733083
1974	3.538159131698144
1975	3.2931280749087435
1976	3.191999704786155
1977	3.338568871680608
1978	3.587845734320218
1979	3.0862538866070404
1980	3.083318272185071
1981	2.867911598423848
1982	2.6225101661037975
1983	2.790386713114465
1984	2.4770330044232725
1985	2.5673386695008134
1986	2.2769953051643195
1987	2.58145757909649
1988	2.5334622944681913
1989	2.5342929199729345
1990	2.1443736730360934
1991	2.2645971018007645
1992	2.1672012229849225
1993	2.763729398464926
1994	2.887957928514129
1995	3.045195011788768
1996	2.872844006746831
1997	2.537275064267352
1998	3.0464411913175167
1999	2.903275888837137
2000	2.740589466253183
2001	2.286892862809093
2002	2.06153913634669
2003	1.8960015017833676
2004	1.8009905447996404
2005	1.8680313673600437
2006	2.3440519440364844
2007	2.507020774051963
2008	2.1685789328172516
2009	1.902183721349936
2010	2.668800330373735
2011	3.084412791797836
2012	3.546637207538459
2013	3.5500522532222827
2014	3.34473292744644