Year	% of total fuel combustion
1971	0.887797506611258
1972	1.312670920692799
1973	1.5828814304558112
1974	1.5360983102918588
1975	1.6726711271230055
1976	2.0604236601458528
1977	2.3628435249974693
1978	1.5363128491620082
1979	1.2373174956693858
1980	3.233256351039261
1981	3.3272422719658903
1982	3.3160542765665517
1983	3.2274295572167935
1984	3.0449141347424042
1985	3.063780589633243
1986	3.5729713051527305
1987	3.4751098966377514
1988	3.240933722384328
1989	3.5047994093034704
1990	3.409434206551292
1991	3.5116533708743916
1992	3.491787229413685
1993	3.5836966574184177
1994	4.50378880469323
1995	4.62563700509604
1996	4.212319790301441
1997	3.9514584835749655
1998	3.784240095479289
1999	3.944548797587238
2000	3.273030506590073
2001	3.1031233171782433
2002	3.011038946136368
2003	2.8129427357067764
2004	2.462850553706241
2005	2.402133286704117
2006	2.11387364115811
2007	2.0680984808800407
2008	1.7271015797659008
2009	1.8010479548941094
2010	1.7755991285403054
2011	1.64760443545575
2012	1.6409685886627141
2013	1.6603166835611165
2014	1.4529508110107254