Year	% of total energy
1971	72.09972892878818
1972	67.68880284294396
1973	67.42170136700706
1974	71.4625146783095
1975	73.62546244229891
1976	74.10833912341752
1977	71.99677686450725
1978	69.87301992154327
1979	68.3960252573384
1980	67.96161510484525
1981	68.43008478928085
1982	66.59801858627871
1983	66.95550430816326
1984	69.64463542220801
1985	71.13631377422335
1986	71.0838905289787
1987	70.38633366643803
1988	71.148973609519
1989	72.02515767547068
1990	70.58775435618332
1991	69.79867965168121
1992	70.36893486402529
1993	64.5450512965742
1994	62.8611208335253
1995	60.82722038278165
1996	58.60279536758134
1997	58.36165982393997
1998	56.56169065235962
1999	55.60213906119981
2000	53.352441036043416
2001	53.0578818971717
2002	52.34695163374106
2003	50.195883661472394
2004	51.055697399290736
2005	51.16753499664303
2006	51.9636174121834
2007	50.7304190067323
2008	50.36008234936061
2009	52.432977317947916
2010	51.0424914074372
2011	47.02892893103471
2012	49.566813892419795
2013	47.41573965493783
2014	45.235559206325135