Year	% of total fuel combustion
1990	11.111111111111112
1991	10.980392156862745
1992	11.681772406847934
1993	12.523481527864746
1994	14.134615384615385
1995	12.669126691266912
1996	39.81042654028436
1997	34.489051094890506
1998	25.45824847250509
1999	25.570776255707766
2000	20.518358531317492
2001	34.02366863905325
2002	42.90780141843972
2003	41.05960264900662
2004	37.49999999999999
2005	37.19211822660099
2006	34.73451327433629
2007	37.981651376146786
2008	37.25910064239829
2009	41.02079395085066
2010	45.29058116232464
2011	38.82352941176471
2012	37.065052950075646
2013	42.45142002989536
2014	42.2279792746114