Year	% of total energy
1971	29.250017305444945
1972	28.012864109635427
1973	26.097884147603416
1974	25.168907772877397
1975	24.81681111939858
1976	23.571924383427174
1977	22.86045097649464
1978	21.737672763438614
1979	21.15828007922401
1980	20.538511717326553
1981	20.223219130229765
1982	20.195733180681113
1983	21.364558752226586
1984	21.960281022333277
1985	21.761271176085497
1986	21.1823203333961
1987	21.114419420441035
1988	20.493973493619084
1989	20.148922980675824
1990	15.548291666686243
1991	14.985358612028362
1992	14.481399020699676
1993	14.214970933392104
1994	13.949768728521184
1995	13.902446731607688
1996	13.452163494418658
1997	12.847492813543912
1998	12.709557149981013
1999	12.861781333625842
2000	12.287524388890079
2001	12.212573602178816
2002	12.58795469593122
2003	12.717427733313302
2004	12.524505964129215
2005	12.4037488335849
2006	12.333464300408608
2007	12.720126631655852
2008	12.73752548227731
2009	12.900285740263705
2010	13.033204533479084
2011	12.669667693770023
2012	12.204033561295795
2013	12.27621325293666
2014	13.026789904521458
2015	4.975748883979628