Year	% of total fuel combustion
1971	10.769230769230768
1972	10.3515625
1973	9.94219653179191
1974	10.486073184052433
1975	10.458452722063036
1976	10.52417716375457
1977	10.873377762188706
1978	11.05105105105105
1979	10.545344983428745
1980	10.299625468164793
1981	11.010299166257969
1982	11.183618361836185
1983	11.489455184534272
1984	13.116670563479076
1985	13.287026663679137
1986	15.348837209302328
1987	16.266849440255882
1988	15.396441906435317
1989	15.035799522673033
1990	15.22491349480969
1991	13.231042917500554
1992	13.031761308950916
1993	12.425671519376667
1994	12.522851919561246
1995	12.321161648515906
1996	12.169110645591317
1997	11.520815632965165
1998	9.128630705394192
1999	10.763052208835342
2000	9.97588908981314
2001	11.048663468128854
2002	10.22652874165248
2003	8.621566632756869
2004	6.787330316742081
2005	8.351383874849578
2006	7.228308777232087
2007	5.938842557493049
2008	7.461115658987254
2009	7.016670813635232
2010	5.78495074407881
2011	5.893385982230996
2012	5.095189919985285
2013	5.2188856729377715
2014	5.34890035297312