Year	% of total energy
1971	6.72353123146164
1972	6.357714774794301
1973	5.890920287543635
1974	6.5075807427676295
1975	5.262901580790631
1976	4.8766535118193985
1977	5.189982940758467
1978	5.379929067376743
1979	4.687972823424939
1980	5.146751680110204
1981	5.088720988797042
1982	4.674987983655581
1983	4.930255883085921
1984	4.804160324919083
1985	4.9166888477936785
1986	4.0386119035800325
1987	4.105327359225232
1988	3.8115472644488677
1989	3.3602838398600685
1990	2.8270183523791483
1991	3.037543427159873
1992	3.0632139939384606
1993	3.330337631673365
1994	3.70073199997192
1995	4.151984985764401
1996	4.045537160731687
1997	4.133311204722594
1998	4.579645188155017
1999	4.570166067428031
2000	4.31278831985404
2001	4.646544858704668
2002	4.511174563521657
2003	4.537872480570285
2004	2.2615118885204994
2005	2.4201581469926414
2006	2.8845702252682384
2007	2.8125428858444623
2008	2.188008843050912
2009	2.30632335282017
2010	2.6267345442253327
2011	2.9543993655187157
2012	3.144097214090358
2013	2.9722689840307583
2014	3.2450043301572538