Year	% of total energy
1971	16.274520269758654
1972	16.520602693542546
1973	16.92812796170802
1974	17.31905344323318
1975	17.312588158744425
1976	17.407393823957683
1977	17.947758307845522
1978	17.872634216768883
1979	16.715378231952506
1980	17.668050790902914
1981	19.89006705650481
1982	21.167428499223735
1983	23.772335114877897
1984	25.87479339499698
1985	28.004831275753123
1986	29.465673073984366
1987	28.05674957706615
1988	23.74243965238685
1989	23.394598559405644
1990	23.6723131213205
1991	22.491951769028784
1992	21.09113905329282
1993	22.05214602085388
1994	21.95145017630817
1995	19.56437900199728
1996	16.9576146065458
1997	16.792653524568966
1998	14.91617178680552
1999	13.693311661825597
2000	13.478225059179033
2001	15.32924650802578
2002	16.263448806264886
2003	16.877151326725794
2004	15.342757467590976
2005	14.983846884017316
2006	14.902864699849685
2007	15.763114681078513
2008	23.24778846017249
2009	24.181673135452254
2010	30.606560575086828
2011	28.877819807365523
2012	28.19012320733702
2013	29.645293471421176
2014	33.681261831460176