Year	% of total fuel combustion
1971	28.36581709145427
1972	28.720626631853786
1973	30.177360459050604
1974	28.19028441983388
1975	28.24622531939605
1976	28.134424816889272
1977	26.52043868394816
1978	26.13037951697839
1979	25.99825632083697
1980	23.376825100963032
1981	24.963924963924963
1982	25.393050601136213
1983	23.981091094927812
1984	23.544271820133883
1985	24.098915198880203
1986	23.080423160050053
1987	22.557224967227988
1988	23.09759140197678
1989	22.990075571337524
1990	11.993748604599242
1991	11.220757124627816
1992	12.237355701353707
1993	12.392250225761433
1994	12.040763894836001
1995	18.680269155632732
1996	16.7734103562309
1997	14.639666949597833
1998	17.161955691367456
1999	16.94859762086653
2000	16.46644126321847
2001	15.95592093755466
2002	16.712235133287763
2003	19.73317745762129
2004	19.916957316060458
2005	20.227957986812896
2006	21.152537980629074
2007	22.041187919884464
2008	20.559830277698616
2009	19.3645440719434
2010	18.538730698853968
2011	19.65312642628937
2012	18.450085209435827
2013	17.32750930511551
2014	17.67019298192128