Year	% of total energy
1971	82.5440386746231
1972	82.22275209451186
1973	81.57371027801402
1974	81.60831119478824
1975	82.02718661841531
1976	81.77173356535725
1977	81.31931664829607
1978	81.5548102406962
1979	81.84899682184879
1980	81.70170606853586
1981	81.96785354631164
1982	82.09791335976281
1983	83.23939781531229
1984	83.15527269088923
1985	83.16385154435682
1986	83.02472924229862
1987	82.8878089349973
1988	82.89988639454414
1989	82.80590535595024
1990	66.18244259930827
1991	66.7449315726773
1992	66.94832998910918
1993	67.19911661034676
1994	66.91472875554894
1995	66.20581271637295
1996	65.96083426555438
1997	65.80064238514635
1998	66.59742122475971
1999	65.60471206214532
2000	66.21056920814783
2001	66.15542089840521
2002	65.29519418099856
2003	65.51518074632689
2004	64.59381324693126
2005	64.45623874214994
2006	63.60249323317221
2007	63.120856112363754
2008	62.99000557484274
2009	62.929202693438306
2010	62.1082753633958
2011	61.7026536639991
2012	57.21554108012614
2013	57.566429852147365
2014	57.67590412876665