Year	% of total energy
1971	87.81230442623233
1972	86.97807144404365
1973	85.02366945889423
1974	84.48495016229592
1975	83.7110139398035
1976	82.42570403728169
1977	80.50188027017828
1978	79.10184018845521
1979	78.72676070956027
1980	77.72567638784075
1981	76.56082404209015
1982	75.43597622412133
1983	76.40039956635002
1984	77.93289553567038
1985	77.50775925945857
1986	78.20512596195398
1987	77.59674940648769
1988	77.87819229412015
1989	77.3723732050867
1990	72.92125662535562
1991	71.86433889263084
1992	70.92092460464347
1993	71.34642056981299
1994	74.26830275610935
1995	74.07822417559643
1996	72.72947596888991
1997	72.225621898853
1998	73.11321882528594
1999	71.86002827528372
2000	71.76647643257623
2001	70.58608721180899
2002	70.32547004318819
2003	69.3103187634499
2004	68.53255117421234
2005	68.17320033867603
2006	68.99753733583596
2007	68.51941529403038
2008	68.51454382204732
2009	70.52032610358448
2010	68.3143555522882
2011	67.08381880619271
2012	66.35924257657993
2013	66.74135478211032
2014	66.1584840641699