Year	% of total fuel combustion
1971	3.759474482061647
1972	3.6850515713524787
1973	3.5133348027330835
1974	3.5381591316981438
1975	3.293128074908744
1976	3.1919997047861552
1977	3.338568871680608
1978	3.5878457343202177
1979	3.0862538866070404
1980	3.0833182721850716
1981	2.8679115984238477
1982	2.622510166103797
1983	2.7903867131144655
1984	2.4770330044232733
1985	2.5673386695008134
1986	2.276995305164319
1987	2.5814575790964898
1988	2.5334622944681913
1989	2.5342929199729345
1990	2.1443736730360934
1991	2.2645971018007636
1992	2.1672012229849225
1993	2.763729398464926
1994	2.887957928514128
1995	3.045195011788769
1996	2.872844006746832
1997	2.5372750642673525
1998	3.046441191317516
1999	2.903275888837137
2000	2.740589466253183
2001	2.2868928628090925
2002	2.06153913634669
2003	1.8960015017833678
2004	1.8009905447996402
2005	1.868031367360044
2006	2.3440519440364844
2007	2.5070207740519628
2008	2.1685789328172516
2009	1.9021837213499364
2010	2.668800330373736
2011	3.084412791797836
2012	3.5466372075384585
2013	3.5500522532222822
2014	3.3447329274464397