Year	% of total energy use
1971	0.39462511698641733
1972	0.3782432684635288
1973	0.7235010206634614
1974	1.9347358963037353
1975	3.070112190078907
1976	2.9612508224188105
1977	2.4159764195538926
1978	3.6517794276277966
1979	3.937545440015311
1980	4.5734643817737135
1981	4.890516608893182
1982	4.870404994572467
1983	5.909089137584312
1984	6.738568199253936
1985	7.928157139407066
1986	7.511896380674334
1987	7.700671707870583
1988	5.860056516985432
1989	5.2210756961840294
1990	6.773688725241976
1991	6.572841226140031
1992	6.386190009972801
1993	7.257551576496289
1994	7.610626658015994
1995	6.936594495015889
1996	6.432940145861712
1997	7.238905028524917
1998	6.760790927687797
1999	5.712306773689651
2000	6.031399086680399
2001	7.745261830101861
2002	7.411579028417988
2003	7.425496954280835
2004	6.439838300998469
2005	6.4242354313027255
2006	6.770591046884038
2007	5.774867856147445
2008	5.428880570397129
2009	6.1853416025756145
2010	5.683269590177278
2011	5.859038801328978
2012	5.570560953711413
2013	5.671430156529576
2014	5.501503642661375