Year	% of total energy
1960	0
1961	0
1962	0
1963	0
1964	0
1965	0
1966	0
1967	0
1968	0
1969	0
1970	0
1971	0
1972	0
1973	0
1974	0
1975	0
1976	2.6654481364486386
1977	2.746170437069265
1978	2.6805718884854968
1979	3.0984203463341
1980	3.1867798046285944
1981	3.5325176407097945
1982	3.553508745222174
1983	3.634807127982835
1984	3.685492799710822
1985	4.045666291318699
1986	4.164071592709288
1987	4.323298586541595
1988	4.438784384408553
1989	4.353614668740488
1990	4.325507737358217
1991	3.902641657799244
1992	3.7818649555805455
1993	3.8755709014675017
1994	4.312348938141861
1995	4.220173783131307
1996	4.240651034311857
1997	4.215942528620304
1998	4.439310230067272
1999	5.0336875204664535
2000	4.516496119603483
2001	3.7844475558791264
2002	4.327476849840699
2003	4.038194158454335
2004	3.965014759611205
2005	4.115615089747345
2006	3.9385247730948634
2007	3.8506019833748204
2008	3.5452828418402085
2009	3.5708288640522627
2010	3.891233285372797
2011	4.526367856715309
2012	4.048771072590113
2013	3.362953947698269
2014	3.129030275192081
2015	3.2509892554122968