Year	% of total energy
1971	8.358446711087769
1972	7.668712120058323
1973	8.501691174946384
1974	7.37479710131677
1975	6.842807392428465
1976	6.161754246667967
1977	6.10180262483066
1978	5.681070085488731
1979	5.576437588849546
1980	5.260102150692211
1981	4.564131683529462
1982	4.40375142167145
1983	3.891882828447848
1984	3.6641911123489144
1985	3.6782263489066636
1986	3.7082750048684
1987	3.608105890507786
1988	3.6145077358370616
1989	3.303793618035976
1990	3.2780946664463517
1991	3.473551565543123
1992	3.433495772377922
1993	3.4122610781755256
1994	3.759295999331565
1995	3.38960986315109
1996	3.2574856254582834
1997	3.187133940436632
1998	3.02637430544727
1999	3.0135460738878974
2000	3.218359902348871
2001	2.918915698048911
2002	2.882906227686052
2003	2.82954297493312
2004	2.6665713456492917
2005	2.330504463097971
2006	2.244799517738524
2007	2.132282281792419
2008	2.0889164291060065
2009	2.079481275807537
2010	2.1620274661154992
2011	2.1040034231005804
2012	2.0924609376791836
2013	2.2326119886241447
2014	2.288710717356881