Year	% of total energy
1960	2.21776560808101
1961	2.100977034812529
1962	1.9302937680643883
1963	1.8007569358728974
1964	1.6925317985405355
1965	1.705012576028642
1966	1.6381041306251505
1967	1.5530237197993326
1968	1.409081018530103
1969	1.356461871750257
1970	2.5365710243088
1971	2.3842036775020428
1972	2.311147849151685
1973	2.218480248922762
1974	2.2902150003293404
1975	2.3020975816733085
1976	2.1136895366249435
1977	2.0988680889081115
1978	2.078311313392582
1979	2.0582336329235464
1980	2.130135656265494
1981	2.279043786227095
1982	2.3467705933643797
1983	2.479542588153205
1984	2.5621569347174296
1985	2.6103261303541423
1986	2.5831940080764246
1987	2.5536666251833946
1988	2.6047211091461064
1989	2.8418207934290414
1990	2.7381418431134597
1991	2.866030906561497
1992	2.9380465777976053
1993	3.1810730829746854
1994	3.16016198138785
1995	3.162710182538523
1996	3.2682610070257234
1997	3.4393774969632376
1998	3.460566066788182
1999	3.459352733187565
2000	3.5129984891846324
2001	3.4263517444871217
2002	3.5238580580239804
2003	3.7743758337720736
2004	3.80466795093903
2005	4.084310875101746
2006	4.304174369018542
2007	4.689075780837015
2008	4.983410159357533
2009	5.545629707922123
2010	5.838484520901276
2011	5.729830878904588
2012	6.210886981167918
2013	6.293898106971926
2014	6.3481034496539985
2015	6.2519603763557665