Year	% of total fuel combustion
1990	14.18757467144564
1991	15.254901960784311
1992	20.39274924471299
1993	26.487163431433935
1994	17.5
1995	5.781057810578105
1996	7.898894154818326
1997	15.145985401459855
1998	20.36659877800407
1999	19.863013698630137
2000	24.838012958963283
2001	19.23076923076923
2002	16.666666666666664
2003	16.55629139072848
2004	17.5
2005	17.48768472906404
2006	15.04424778761062
2007	13.577981651376147
2008	18.629550321199144
2009	17.202268431001887
2010	19.03807615230461
2011	17.81512605042017
2012	20.42360060514372
2013	18.83408071748879
2014	21.761658031088082