Year	% of total fuel combustion
1971	30.68513119533528
1972	31.276005547850207
1973	32.58426966292134
1974	32.32387631495059
1975	30.127795527156554
1976	31.643625192012284
1977	26.887770210245776
1978	23.942420681551116
1979	22.6089588377724
1980	22.658522396742292
1981	22.09912536443149
1982	22.408627920910725
1983	21.956145412579346
1984	20.059612518628914
1985	19.183313748531138
1986	19.562682215743436
1987	18.147502903600465
1988	18.311403508771935
1989	19.079837618403246
1990	18.92904953145917
1991	18.390146089945578
1992	17.107884998576715
1993	15.83357411152846
1994	16.510067114093957
1995	14.677775055133544
1996	13.554146112285645
1997	14.478554321794032
1998	13.982193443949818
1999	14.74903474903475
2000	14.521266629192429
2001	13.508740950026489
2002	13.579646734726948
2003	13.184392699811204
2004	13.331384300540858
2005	13.23162274618585
2006	13.491139567973095
2007	13.794738089594691
2008	13.122017723244715
2009	14.440355055206755
2010	14.83185117039763
2011	15.131959160084758
2012	15.17540751240255
2013	15.223405147120463
2014	14.567334336157074