Year	% of total fuel combustion
1990	11.500701262272091
1991	12.742958112462322
1992	13.048485546470115
1993	12.568015925680163
1994	10.513982190282768
1995	11.731647348085703
1996	12.541082857637086
1997	13.095033510912529
1998	14.300941552673654
1999	13.12869822485207
2000	12.396852811360583
2001	12.043222003929273
2002	13.01693580149665
2003	13.295697878138993
2004	12.835108336393683
2005	14.142883112161424
2006	15.970644766730738
2007	16.69059583632448
2008	18.069815195071868
2009	18.440350563405474
2010	18.27597728032075
2011	19.884068153873176
2012	20.231914157147802
2013	21.39423076923077
2014	20.511927563990945