Year	% of energy use
1971	5.429332002643691
1972	3.5759007409807153
1973	5.26641894582896
1974	4.477276911601765
1975	-0.8957420639636329
1976	-2.409944174922724
1977	-0.27201897255831325
1978	0.32786184058958073
1979	3.7344830724461002
1980	2.838054820495989
1981	2.9329092788732414
1982	4.584908101230455
1983	6.50209444662015
1984	7.0591974076305775
1985	6.398492170520423
1986	5.853318966968527
1987	2.7893833706016444
1988	-4.245596405382792
1989	-8.806387778250873
1990	-10.493237724706423
1991	-14.931160847170187
1992	-15.684721116588822
1993	-19.99518676588994
1994	-27.872087379846914
1995	-28.653826364569085
1996	-27.678850157122312
1997	-27.742168518999463
1998	-27.23598194321011
1999	-29.09780340337797
2000	-33.745153153629445
2001	-34.19088759828692
2002	-36.20910004179034
2003	-34.60577540361605
2004	-27.612904441785847
2005	-23.12319646648288
2006	-20.35421759548885
2007	-22.249683095517497
2008	-18.36674501225295
2009	-19.107389735186093
2010	-24.193456844499778
2011	-27.405909994090702
2012	-12.885422777873902
2013	-15.379065419400707
2014	-10.992737132779514