Year	% of total fuel combustion
1971	26.94780149138596
1972	25.976744186046513
1973	27.073311525880317
1974	26.806407634628492
1975	25.569769151595352
1976	24.57583547557841
1977	22.95288197621226
1978	22.54969949144706
1979	22.36732135394902
1980	20.662371425341924
1981	19.96021220159151
1982	20.035200938691702
1983	19.7153314355429
1984	20.63837776943297
1985	20.88419891026967
1986	22.38573021181717
1987	21.638524077548468
1988	22.893772893772894
1989	22.072653512815787
1990	24.45379133076294
1991	23.472803347280337
1992	22.224376060092073
1993	26.009290742780518
1994	24.25081843364392
1995	25.18815445026178
1996	25.807222200103514
1997	26.07491176805435
1998	26.508515357720206
1999	29.944714357513824
2000	29.158124038954377
2001	29.61650114591291
2002	29.922729260825193
2003	30.029668607254816
2004	30.763447828904734
2005	31.227104034478632
2006	30.590933380833636
2007	30.21753625604267
2008	32.32209199696217
2009	32.14115686741252
2010	32.865884241147555
2011	33.6734693877551
2012	34.70069116326292
2013	34.989164549394715
2014	34.34515995612221