Year	% of total fuel combustion
1971	3.759474482061647
1972	3.685051571352477
1973	3.5133348027330835
1974	3.538159131698144
1975	3.2931280749087435
1976	3.191999704786155
1977	3.338568871680608
1978	3.587845734320218
1979	3.0862538866070404
1980	3.0833182721850725
1981	2.8679115984238477
1982	2.6225101661037975
1983	2.790386713114465
1984	2.4770330044232733
1985	2.5673386695008142
1986	2.276995305164319
1987	2.5814575790964898
1988	2.5334622944681913
1989	2.534292919972935
1990	2.1443736730360934
1991	2.264597101800764
1992	2.167201222984923
1993	2.763729398464926
1994	2.887957928514128
1995	3.0451950117887683
1996	2.872844006746832
1997	2.537275064267353
1998	3.0464411913175162
1999	2.903275888837137
2000	2.740589466253183
2001	2.2868928628090925
2002	2.06153913634669
2003	1.8960015017833678
2004	1.8009905447996404
2005	1.8680313673600437
2006	2.344051944036485
2007	2.5070207740519628
2008	2.168578932817252
2009	1.9021837213499364
2010	2.6688003303737355
2011	3.084412791797836
2012	3.54663720753846
2013	3.5500522532222822
2014	3.3447329274464397