Year	% of total fuel combustion
1990	9.125
1991	8.663251047973917
1992	6.654111738857502
1993	6.3575168287210175
1994	31.596091205211728
1995	30.182926829268293
1996	24.939467312348672
1997	12.589073634204276
1998	13.145539906103284
1999	12.87223823246878
2000	15.233236151603496
2001	15.777777777777777
2002	14.345991561181433
2003	14.089347079037799
2004	15.734035549703753
2005	14.501891551071877
2006	16.48540354894104
2007	16.558089033659062
2008	16.699604743083004
2009	17.268678871845623
2010	16.593460224499758
2011	14.572649572649574
2012	14.734411085450347
2013	13.11018131101813
2014	13.737280296022202