Year	% of total energy
1971	82.81463757171335
1972	77.3285485231518
1973	78.19830497970314
1974	77.32530239826116
1975	80.19119059509615
1976	82.27394897648993
1977	84.85843441010186
1978	78.58795578314307
1979	78.97852144394419
1980	78.91553842084375
1981	79.72655903867636
1982	82.1857168964607
1983	81.3091483665978
1984	81.8361829296287
1985	78.48434094583556
1986	78.91438197336721
1987	78.44959641812503
1988	76.86138962269466
1989	76.78644034264276
1990	54.24552740059927
1991	54.20778178634574
1992	55.167042968763546
1993	54.50629520082988
1994	54.8220156630242
1995	56.06003880487043
1996	55.676438863196644
1997	55.5576693065937
1998	56.788718690831786
1999	55.15198191283021
2000	54.855397633039814
2001	53.7730213771596
2002	52.65423993325595
2003	49.98383366755554
2004	49.752509854130075
2005	52.68877681086216
2006	49.1068083975425
2007	47.04657913882026
2008	44.383971276176744
2009	41.696725522280964
2010	40.567904024786884
2011	39.84850140526021
2012	37.03529557331512
2013	37.71359051271661
2014	36.37610660964302