Year	% of total fuel combustion
1971	29.69399319984889
1972	27.620783956244306
1973	27.172797889491424
1974	27.13308197179165
1975	25.656201749871332
1976	26.34564185669638
1977	22.198559983774466
1978	23.482309124767223
1979	24.680359646952073
1980	23.33359878951979
1981	22.521699406121513
1982	20.826345479493824
1983	19.860552041403103
1984	17.972258916776752
1985	17.509152803648277
1986	17.624190064794814
1987	18.735891647855528
1988	18.98707794914548
1989	19.497907949790793
1990	22.191532519097148
1991	23.897231346785546
1992	22.836215961419917
1993	23.43110054168318
1994	24.181129308237598
1995	23.167385339082713
1996	22.899082568807337
1997	21.49553626936563
1998	22.589002416091752
1999	22.532342125453052
2000	22.19082254291075
2001	21.122778675282714
2002	19.72551809606867
2003	18.92966500616974
2004	17.54672236364032
2005	16.183252825074863
2006	17.018620170057044
2007	15.373493975903616
2008	15.869280510763689
2009	13.790767636921483
2010	14.239288307915762
2011	13.967152521096313
2012	13.265075529751247
2013	13.076304659372925
2014	13.655976471002626