Year	% of total fuel combustion
1971	9.305186075116564
1972	8.914044101905374
1973	9.030335336305487
1974	8.830418665999591
1975	9.12183055040198
1976	9.065775356936536
1977	8.934187765371913
1978	8.561763462210212
1979	8.379226211223424
1980	8.640977728397557
1981	8.999782452265007
1982	9.198039248048325
1983	9.508125094526696
1984	9.573500471315882
1985	9.55963780861182
1986	9.520698184533533
1987	9.623793108594109
1988	9.905971747517274
1989	9.753621323266554
1990	9.957377478434168
1991	9.678233438485806
1992	9.799250977584403
1993	9.698052864264888
1994	9.37436728082608
1995	9.470925104659685
1996	9.105652838171347
1997	8.579776872675756
1998	8.376769217730317
1999	8.467240224176619
2000	8.44392547088389
2001	8.32060602358116
2002	8.278071602929211
2003	7.84836413374467
2004	7.638386912687844
2005	7.389970621762137
2006	7.478444008424388
2007	7.31480596651869
2008	7.204364743698189
2009	7.229166485951962
2010	6.993541048868669
2011	6.687994769166103
2012	6.625812134398362
2013	6.670069008365322
2014	6.551766464255544