Year	% of total fuel combustion
1971	21.46788990825688
1972	20.173160173160174
1973	20.17479970866715
1974	18.968253968253965
1975	17.387687188019967
1976	18.01405975395431
1977	16.588419405320806
1978	17.158385093167702
1979	17.647058823529413
1980	17.660728117738188
1981	17.63848396501458
1982	20.413026211278794
1983	20.788824979457683
1984	21.136173767752716
1985	22.084805653710248
1986	22.488888888888887
1987	22.40943555181129
1988	18.98332009531374
1989	16.630669546436284
1990	16.05019815059445
1991	16.311584553928096
1992	15.121344119477289
1993	14.912280701754385
1994	15.052436767427514
1995	16.47555823777912
1996	17.323290845886444
1997	17.653569452130604
1998	17.898627243928193
1999	18.158168574401667
2000	18.079625292740047
2001	16.558300823580407
2002	17.378681045209458
2003	15.677491601343785
2004	16.922514619883042
2005	16.4913471326773
2006	16.217870257037944
2007	15.468660149511212
2008	17.151607963246555
2009	19.284977655551735
2010	18.437197287697774
2011	17.868538608806638
2012	17.335058214747736
2013	17.028535980148884
2014	17.330861909175162