Year	% of energy use
1971	19.433030682245057
1972	17.597788032969213
1973	17.226332014181235
1974	17.546206527799445
1975	22.267184661261837
1976	20.51725206843394
1977	15.28883560982646
1978	-16.208530474129628
1979	-34.66390484896713
1980	-28.536047243526546
1981	-28.61224941286934
1982	-29.609408074068057
1983	-28.08997124494008
1984	-34.59924610973292
1985	-38.5867541316307
1986	-29.337272797632775
1987	-16.62191582298062
1988	-6.235658589021578
1989	-7.407156266547488
1990	-8.854998297252036
1991	-2.937454110788432
1992	-3.3420315602095005
1993	-1.5722153260985565
1994	1.582944195968658
1995	8.665523855253985
1996	11.865159160552796
1997	10.916223231982185
1998	14.93843473048854
1999	22.269879012832163
2000	23.40871147866232
2001	20.19108504898066
2002	21.753024575520953
2003	18.318353050171705
2004	25.379457706185477
2005	20.01021200650244
2006	12.070384276538539
2007	12.971325874588135
2008	15.935571056166816
2009	4.243178344896264
2010	-3.737478039107582
2011	-23.024166105746815
2012	-14.18641290690994
2013	-18.91873807529164
2014	-14.899588143100317