Year	% of total energy
1960	2.8159195272645183
1961	2.709368140910983
1962	2.5690484215097418
1963	2.4450099828950007
1964	2.3377137998777195
1965	2.2416240289215006
1966	2.1644595822070936
1967	2.0500030808405
1968	2.020681586930326
1969	1.9460601127835198
1970	2.23484364817633
1971	2.249490733240238
1972	2.188459052796499
1973	2.123031473660238
1974	2.1981577510348336
1975	2.172986469766718
1976	2.1930915466306877
1977	2.2360812584820597
1978	2.3555836888261847
1979	2.411032433209662
1980	2.549725917658424
1981	2.655924771563995
1982	2.8757773506725606
1983	3.035296165462161
1984	3.1612852332417822
1985	3.125084880111446
1986	3.1295288662735605
1987	3.2318704167518235
1988	3.158347696620862
1989	3.1477478215941614
1990	1.9664357486822008
1991	2.0109324044208177
1992	2.117563421039675
1993	1.9447853756763303
1994	1.9389622537146014
1995	2.033145108952306
1996	2.014554102014216
1997	2.0025127777921647
1998	2.0794066440060526
1999	2.3502613024301398
2000	2.3570852147103487
2001	2.205609371528271
2002	2.161691484021042
2003	2.3138540162798056
2004	2.36688706156408
2005	2.5255075092928143
2006	2.6983397490979018
2007	2.8296535207429594
2008	3.019185432628416
2009	3.2019584345279952
2010	3.4148819842582876
2011	3.429371994770172
2012	3.681281493216492
2013	3.7905825473533894
2014	3.8560846020459576
2015	3.8972240414877724