Year	% of total energy
1960	2.5609003409713598
1961	2.474812638305736
1962	2.3082077528719345
1963	2.1485888529627055
1964	2.0552730851272463
1965	2.0217520135229248
1966	1.960953899790787
1967	1.8798769262976658
1968	1.736224521593925
1969	1.6499257102143283
1970	2.518469914355586
1971	2.3992085283537894
1972	2.3624537526499982
1973	2.2803529801051363
1974	2.357922657584376
1975	2.401057297181069
1976	2.2698215719834467
1977	2.2575792600273865
1978	2.2637546223449685
1979	2.255476495503041
1980	2.3378399449100997
1981	2.490180868991759
1982	2.566108369813346
1983	2.6800544444945715
1984	2.7367369737814093
1985	2.7462032820729307
1986	2.724671167748162
1987	2.6912750605084153
1988	2.7315019621760204
1989	2.962274049508875
1990	1.9780748246650937
1991	2.0154800235971537
1992	2.1187219975193177
1993	2.3092222839109025
1994	2.280761923919824
1995	2.29976985898607
1996	2.3700044328108545
1997	2.465643195775536
1998	2.4613437316983164
1999	2.4797932087779735
2000	2.4565056150690925
2001	2.4000580904422644
2002	2.4335977486152296
2003	2.5353814637446845
2004	2.5354127006233456
2005	2.6852813573696137
2006	2.7837301766537004
2007	3.006390559571985
2008	3.159005317239761
2009	3.500403168566179
2010	3.619335702543612
2011	3.452182270839139
2012	3.658249429617125
2013	3.7465176197813763
2014	3.8743049942491665
2015	5.475260799679647