Year	% of total energy
1971	84.35700098942036
1972	83.3573638948886
1973	82.07292776661428
1974	83.72627626541517
1975	81.70833474676887
1976	80.88196166732278
1977	76.02583452850695
1978	73.34366088607668
1979	74.07383026916638
1980	74.28869661656894
1981	75.18346272101894
1982	75.1587445872358
1983	76.87561433191765
1984	74.51770734357753
1985	73.80366205077145
1986	73.48697990033668
1987	74.32692870530207
1988	72.6964834047618
1989	69.98891159111713
1990	68.9828176592763
1991	67.49517497831941
1992	65.86827243450345
1993	61.45629340133556
1994	57.67417419678925
1995	58.9157732656273
1996	60.106097658423295
1997	57.82972646209799
1998	55.18926508792491
1999	52.89665195558821
2000	56.69807856991883
2001	56.30925188558733
2002	53.64309953543047
2003	53.12685814806278
2004	52.32210237403325
2005	53.21222330681894
2006	48.716740859764144
2007	47.0345107446428
2008	46.88323304382202
2009	47.04732296956195
2010	45.07991676052428
2011	43.02305215088189
2012	41.70979401135436
2013	40.70535110693713
2014	40.36902411108456