Year	% of total fuel combustion
1971	25.921754994481862
1972	25.381240415743743
1973	25.57671855361114
1974	26.392265193370164
1975	26.437325854564666
1976	27.16718662097887
1977	27.07577114022951
1978	26.929842003028405
1979	26.70571473800855
1980	25.878377442630217
1981	24.43348532227625
1982	24.017610544450218
1983	24.66360856269113
1984	24.37275494255395
1985	24.5442557877136
1986	22.672054189060194
1987	24.09195924705526
1988	22.89432059710346
1989	23.168288494562105
1990	22.437555915564477
1991	21.947553227719514
1992	21.216688912413122
1993	21.067066686070593
1994	21.242315030739878
1995	21.257197200715325
1996	21.920312758322233
1997	22.160968218908017
1998	21.445059815856688
1999	21.25275874600037
2000	21.365245209815203
2001	20.90392128613439
2002	21.19826593510804
2003	20.617999484446067
2004	20.822786812630515
2005	20.57226863088903
2006	20.88948988434988
2007	19.890640123661893
2008	20.632435601227627
2009	19.048793550569396
2010	20.80823575305965
2011	20.984091274305
2012	19.23794462496448
2013	19.15720299574135
2014	18.454284320633025