Year	% of total energy
1971	80.34520485492884
1972	80.49870881552285
1973	79.756149877817
1974	80.64900674707988
1975	82.20173293365427
1976	84.39684976763586
1977	84.2183574696077
1978	85.26075392659178
1979	86.77998403190075
1980	84.1556820728919
1981	85.60022637653688
1982	84.07970187709115
1983	85.16352784655307
1984	85.8022845635521
1985	84.16666913093859
1986	84.60511936271314
1987	87.53377215318399
1988	83.81336163552251
1989	85.2287180089819
1990	40.40159226476632
1991	41.04637587117711
1992	41.643111622095304
1993	43.468665077727856
1994	42.215615950830085
1995	42.45587219433806
1996	44.007222140639755
1997	44.04462562277614
1998	44.52651249228944
1999	40.93770547474412
2000	43.679765991859014
2001	42.94223207157194
2002	40.38798819550251
2003	42.490875885735754
2004	43.44584668342479
2005	43.57501674872177
2006	43.19677796285707
2007	41.20908269052218
2008	40.11587601029064
2009	39.89072705642721
2010	39.44344030405853
2011	39.9703217992016
2012	37.97625526059236
2013	38.02311713649974
2014	37.97168171588439