Year	% of total fuel combustion
1981	32.60869565217392
1982	29.86111111111111
1983	30.49645390070922
1984	32.85714285714286
1985	33.33333333333333
1986	29.47976878612717
1987	28.49162011173184
1988	25.581395348837212
1989	22.78481012658228
1990	17.793594306049823
1991	17.94871794871795
1992	20.909090909090907
1993	19.692307692307693
1994	15.584415584415584
1995	12.539184952978058
1996	18.493150684931507
1997	17.915309446254074
1998	25.815217391304344
1999	22.020725388601036
2000	21.339950372208435
2001	24.031007751937985
2002	26.550868486352357
2003	23.017902813299234
2004	16.120906801007557
2005	21.49532710280374
2006	24.205378973105134
2007	28.009259259259256
2008	26.195899772209568
2009	22.505307855626327
2010	17.431192660550458
2011	14.322916666666668
2012	11.65644171779141
2013	11.450381679389313
2014	10.029069767441861