Year	% of total fuel combustion
1971	24.054067386907406
1972	23.328746975376003
1973	22.675897146086466
1974	22.5577731092437
1975	21.95271596858639
1976	20.685524383646335
1977	20.872521246458927
1978	22.119460500963392
1979	21.827861579414375
1980	21.797677158727492
1981	20.323126634866902
1982	17.043398339891432
1983	16.53798391015604
1984	15.513652807374003
1985	15.675777657241232
1986	14.791386854988954
1987	14.586157403715813
1988	14.39241055430867
1989	14.47176732838362
1990	13.76442267784511
1991	13.36940680331173
1992	13.331167584648776
1993	13.059512414841505
1994	12.882183448055065
1995	13.01891215040896
1996	13.683616350722046
1997	13.27392172390332
1998	13.600860064065994
1999	13.216458614770502
2000	12.856527190095594
2001	12.651684745534725
2002	12.548249979072299
2003	12.615014971286072
2004	12.654827763322977
2005	12.519080289859732
2006	12.150018846588768
2007	13.00303003236157
2008	13.631146471892528
2009	13.187270129079112
2010	13.535789820255692
2011	13.922110271927444
2012	13.7102409999401
2013	13.531803659599188
2014	12.980589106349575