Year	% of total energy
1971	28.892483384008383
1972	27.66355063232575
1973	25.79506667435349
1974	24.955832314794755
1975	24.77705919890987
1976	23.51852786292637
1977	22.867676590051982
1978	21.907121080852352
1979	21.347438494510364
1980	20.664800676888156
1981	20.42811676161169
1982	20.398095975138435
1983	21.430782246308077
1984	22.131327435030162
1985	21.965322285543255
1986	21.442630833074066
1987	21.359766661367143
1988	20.83677738963406
1989	20.59666346724823
1990	16.22718137105795
1991	15.624906673025537
1992	15.106744529436643
1993	14.63298325437479
1994	14.337890307153598
1995	14.210469589788325
1996	13.801583071991569
1997	13.171769785325601
1998	12.99103195637443
1999	13.142418872560457
2000	12.576326176801551
2001	12.509409871671625
2002	12.787477208294732
2003	12.856441873788878
2004	12.666056226432756
2005	12.467657824136454
2006	12.352169673050701
2007	12.709535048331647
2008	12.706266834336146
2009	12.857399389738543
2010	12.951785060773195
2011	12.631961663905694
2012	12.175489978799373
2013	12.246174502323075
2014	13.002217191749807
2015	4.975748883979628