Year	% of total fuel combustion
1971	28.038879359634077
1972	27.93143337890419
1973	28.380187416332
1974	28.664093932178336
1975	28.903295515937334
1976	30.646627053477804
1977	32.59818936764005
1978	32.479540201161996
1979	32.96781039971701
1980	33.71891956353228
1981	28.550399999999996
1982	27.80231739325267
1983	26.47376230945636
1984	25.837320574162685
1985	25.995646049430142
1986	24.884106907800607
1987	26.95846110956231
1988	27.44313510550836
1989	26.855563983096758
1990	25.275440976933517
1991	26.139038552074073
1992	25.966991977926522
1993	26.140956136027597
1994	26.097908745247146
1995	25.860706130335497
1996	26.237040048790405
1997	25.964938966422025
1998	25.951659398329515
1999	26.444714633099704
2000	27.802675242037562
2001	26.45297286445612
2002	27.414810839817545
2003	27.513679890560876
2004	26.75210640152371
2005	26.247987117552334
2006	25.994331751743466
2007	27.493629413906078
2008	26.03696570755124
2009	25.14643319563475
2010	25.84136237281732
2011	26.987345671090125
2012	23.965043577112542
2013	21.83546407285135
2014	20.60207554304441