Year	% of total energy
1960	2.773336127653518
1961	2.6679546216652175
1962	2.5305907840478774
1963	2.411861215242012
1964	2.307141347513807
1965	2.2145043364577757
1966	2.1416408397661195
1967	2.0308062046335857
1968	2.0022690627081325
1969	1.9317393350922631
1970	2.20513195159694
1971	2.162020750141086
1972	2.120990074508686
1973	2.0433559696688355
1974	2.1091430142884913
1975	2.0798628502183227
1976	2.0952313562116633
1977	2.127049259732203
1978	2.2205510866023754
1979	2.256492338644937
1980	2.3828864332386814
1981	2.473960289216805
1982	2.661389348149158
1983	2.81269426272823
1984	2.9424781995765947
1985	2.918519132963168
1986	2.9316854541611366
1987	3.0125527358328035
1988	2.929073788541422
1989	2.898793414510737
1990	1.945485792641368
1991	2.008683311845088
1992	2.1055673815559746
1993	2.001950452419269
1994	1.9818570487303961
1995	2.0798856253823037
1996	2.0682847123705823
1997	2.068115442346568
1998	2.1296775965549903
1999	2.3773942427845935
2000	2.3758902909206827
2001	2.219773334816373
2002	2.1852331781158627
2003	2.341031015324172
2004	2.3931689015760425
2005	2.5436283965553352
2006	2.6875244527392748
2007	2.8039261810606346
2008	2.992302264456789
2009	3.1643058733096217
2010	3.350687582702337
2011	3.3703431572323934
2012	3.5827892530319727
2013	3.6844544226876135
2014	3.6705791273806736
2015	3.985735852952455