Year	% of total fuel combustion
1990	26.131889763779526
1991	23.119015047879618
1992	20.509193776520508
1993	18.488529014844808
1994	20.58613295210865
1995	17.861975642760488
1996	17.20136518771331
1997	18.019680196801968
1998	16.628830874006812
1999	15.995397008055235
2000	17.222884386174016
2001	17.295774647887324
2002	15.649867374005305
2003	14.816650148662042
2004	17.39795918367347
2005	17.67955801104972
2006	18.327491236855284
2007	17.57775683317625
2008	18.75
2009	16.054564533053515
2010	15.789473684210527
2011	14.874651810584957
2012	14.137720901889091
2013	14.465408805031446
2014	14.927344782034343