Year	% of total energy
1971	3.508530553358918
1972	3.472309574127766
1973	3.5119270795896287
1974	3.4769733048822644
1975	3.4477212653804457
1976	3.33194468984762
1977	3.2421547323013202
1978	3.095415309768623
1979	2.9666329826548417
1980	2.8340359919659517
1981	2.7958887837387283
1982	2.711775900162121
1983	2.6502904167504937
1984	2.6220001506637574
1985	2.554888953174379
1986	2.586778479426776
1987	2.7123191272458347
1988	2.6909345772409554
1989	2.7295485293821
1990	2.4496689547059725
1991	2.5828193407685385
1992	2.9639609709283192
1993	3.239856621194747
1994	3.566381393337406
1995	3.799902469683933
1996	4.341786157897327
1997	4.315619416885239
1998	4.661109563203848
1999	4.3909437311790604
2000	4.1194212314149246
2001	3.9986597576272307
2002	4.1948888934774535
2003	4.135023368031099
2004	4.067849581074931
2005	3.9308810385973323
2006	3.9174555541525935
2007	4.630722673519357
2008	4.224467836591299
2009	4.299291180423292
2010	4.5450927035765805
2011	6.169501633157582
2012	6.089331502319727
2013	8.03025353174189
2014	7.350265855696183