Year	% of total energy
1971	93.6242549906195
1972	92.69807048638214
1973	90.95995270772855
1974	90.5432741573297
1975	89.11516445806178
1976	86.95745686502833
1977	84.79004831314604
1978	83.12481388043518
1979	82.06575637988185
1980	80.57094277436426
1981	79.12024879948085
1982	77.53621776833846
1983	77.53628150673612
1984	79.5532176338857
1985	79.18750927328176
1986	80.50824544360157
1987	79.80076979984815
1988	79.61193765532599
1989	78.99508168382991
1990	77.57561744219464
1991	75.92980078526674
1992	74.91527598913483
1993	75.62865488266665
1994	79.58422595382261
1995	79.51004178324443
1996	78.30781872237309
1997	77.77342978844271
1998	79.32409873842099
1999	78.68309906619947
2000	77.86591404496271
2001	76.22421591665466
2002	75.88057603338616
2003	73.92492618461453
2004	73.86754585840197
2005	73.21855762728653
2006	74.86395210561862
2007	75.22443488399576
2008	75.17084825419631
2009	78.577676537111
2010	75.94018423477904
2011	74.53545475153476
2012	74.2199906445293
2013	74.87022126725337
2014	74.33917124589031