Year	% of total fuel combustion
1971	25
1972	27.58620689655173
1973	27.55905511811023
1974	30.4
1975	30.82706766917293
1976	28.87323943661972
1977	27.848101265822784
1978	30.379746835443033
1979	32.73809523809524
1980	31.764705882352946
1981	28.57142857142857
1982	27.044025157232703
1983	29.545454545454547
1984	32.795698924731184
1985	30.538922155688624
1986	28.823529411764703
1987	30.526315789473685
1988	33.014354066985646
1989	34.913793103448285
1990	34.862385321100916
1991	35.18518518518518
1992	31.70731707317073
1993	29.230769230769234
1994	26
1995	21.008403361344538
1996	26.136363636363637
1997	19.613259668508285
1998	18.055555555555554
1999	16.972477064220183
2000	23.16258351893096
2001	12.28733459357278
2002	12.98932384341637
2003	13.461538461538462
2004	14.082503556187767
2005	16.201117318435752
2006	20.78125
2007	21.79802955665025
2008	19.289340101522843
2009	17.43243243243243
2010	17.98365122615804
2011	20.88305489260143
2012	31.017964071856284
2013	27.573964497041427
2014	9.714285714285714