Year	% of total energy
1960	5.32752963251266
1961	5.194344888593745
1962	4.910422641004841
1963	4.575784487526765
1964	4.255610651236664
1965	3.748218703064183
1966	3.730092663657716
1967	3.999576358143243
1968	4.395903871613073
1969	4.623280921309777
1970	5.443053898463206
1971	5.393384785609225
1972	4.987945717682468
1973	4.903884618817884
1974	4.778702418240228
1975	3.748994203438501
1976	3.6992564224787707
1977	3.6274832350990014
1978	3.8209736958413796
1979	3.7366381887206925
1980	3.9843179660248134
1981	3.8853792318224856
1982	3.9994523408711977
1983	4.429405428830618
1984	4.224806315965298
1985	4.3920985458150845
1986	4.513817381641007
1987	4.413294833516371
1988	4.226033452237193
1989	3.9634445123536794
1990	4.803451227296295
1991	4.800158955016708
1992	4.683734629838592
1993	4.524679497695186
1994	4.936811280793443
1995	5.046225470146693
1996	4.652839343997432
1997	4.534335927993041
1998	4.827388209193225
1999	4.895889861755178
2000	4.841235008068823
2001	4.515571180124896
2002	4.94417697481357
2003	4.615762429028461
2004	4.921944624342559
2005	4.688056632941544
2006	4.587297305483407
2007	4.618167574150696
2008	4.330790866881751
2009	4.284066949330198
2010	4.169444022558578
2011	4.146999665794883
2012	4.2837652006103015
2013	4.434832133749259
2014	4.148353838181467
2015	4.102835182489143