Year	% of total fuel combustion
1990	17.519685039370078
1991	19.493844049247606
1992	19.519094766619517
1993	19.63562753036437
1994	22.015725518227306
1995	22.124492557510152
1996	23.68600682593857
1997	23.98523985239852
1998	23.041997729852437
1999	24.68354430379747
2000	25.744934445768774
2001	24.676056338028168
2002	24.827586206896548
2003	25.22299306243806
2004	26.785714285714285
2005	27.27272727272727
2006	28.94341512268403
2007	28.934967012252592
2008	30.009920634920633
2009	31.741867785939142
2010	31.907894736842106
2011	31.81058495821727
2012	33.577087141986595
2013	35.15723270440251
2014	36.591809775429326