Year	% of total energy use
1991	18.135895523677345
1992	17.42302128298538
1993	14.990174139668607
1994	11.719812870734113
1995	13.763061922478176
1996	14.02933806191093
1997	13.326603964764116
1998	14.634073897169175
1999	15.817806317218592
2000	15.71474738480337
2001	14.091235801528676
2002	15.93022933964228
2003	16.145484503700047
2004	19.32217339117836
2005	19.065112807251527
2006	19.295502930775854
2007	19.83901153499426
2008	17.570437457960516
2009	18.139592350205472
2010	18.027131182331615
2011	18.538528753115624
2012	18.68085245084935
2013	17.948642817784695
2014	17.785332290756976