Year	% of total energy
1960	23.656051617054004
1961	21.61675598202713
1962	21.53395960924498
1963	19.587100746711215
1964	18.69220548859858
1965	18.858037162048905
1966	18.283257100735593
1967	16.725695727768805
1968	16.54601515380877
1969	14.572312957795946
1970	12.944894356787312
1971	11.186966831176823
1972	10.05228290947885
1973	9.262278537398512
1974	8.71547740474637
1975	8.3590966789545
1976	7.76422572469517
1977	8.317560168005791
1978	8.345054401543086
1979	8.000864831681874
1980	7.192195558868739
1981	7.462882253736586
1982	7.047992932671073
1983	7.449073969271367
1984	7.351701133634873
1985	8.417795203848085
1986	8.392063179559797
1987	8.469960915658163
1988	8.196854762061282
1989	11.902566020425457
1990	14.159908849158956
1991	13.914790209880893
1992	13.040864086279008
1993	13.23336086860071
1994	13.10397045649703
1995	12.247647898838228
1996	11.979090559647213
1997	11.749266380111717
1998	10.813448269544137
1999	10.156393500704834
2000	10.136011970302837
2001	10.03015233922149
2002	9.907336256260962
2003	10.188723809828764
2004	10.020746706061086
2005	9.907226628376966
2006	10.772172125731224
2007	11.191286033488895
2008	11.469130847853243
2009	11.947006473186352
2010	11.299202696534811
2011	11.671555666324425
2012	10.74575398047714
2013	10.850894793287424
2014	10.558484080122142
2015	10.358604691649589