Year	% of total fuel combustion
1971	21.596575105425742
1972	21.32985313398367
1973	20.83111532853473
1974	20.31870250652149
1975	20.465563640956386
1976	19.931858489685432
1977	19.983015632214233
1978	18.922859350624734
1979	19.02602890827567
1980	18.139023317201936
1981	18.891943889548216
1982	18.794263518724218
1983	18.87256222389829
1984	18.559929824994903
1985	20.02103722111842
1986	19.392148832855554
1987	18.9225221287291
1988	18.860396260469265
1989	18.052684685390727
1990	17.911885699972064
1991	16.898703792606813
1992	15.160174791919598
1993	14.31094127111826
1994	12.67094149314687
1995	12.216495559527273
1996	10.283800298737157
1997	11.471134659051813
1998	9.256623184395721
1999	9.813583635636354
2000	8.881148337761651
2001	8.563851111727882
2002	8.108540874388815
2003	7.611125642177159
2004	7.462184233587765
2005	6.819780929398349
2006	6.495481051534954
2007	6.156229274785618
2008	5.798458949713097
2009	5.573417247705377
2010	5.401937187380385
2011	5.205434140578854
2012	5.302651557771341
2013	5.3062251735277846
2014	5.358337661880321