Year	% of total energy
1971	4.9042870959906955
1972	4.757490118016689
1973	4.263710233876314
1974	3.7992828667142238
1975	3.555688470657683
1976	3.217334122522818
1977	3.0632801007717276
1978	2.8980117926359927
1979	2.607824099114628
1980	2.5674367991515403
1981	2.399305272580898
1982	2.1810385442223112
1983	2.203976755737474
1984	2.0666220132301816
1985	2.0268225238839146
1986	2.002525267560119
1987	1.9617503773255254
1988	1.9579431698011533
1989	1.7673478319652383
1990	1.6122024927734977
1991	1.6434748944566662
1992	1.5631152454191937
1993	1.4969882295863313
1994	1.4590338592947782
1995	1.4010766719725922
1996	1.4317826822044832
1997	1.333688263441645
1998	1.3608324343897105
1999	1.3190077622927863
2000	1.3385533205179614
2001	1.2668753522307687
2002	1.2538624341535147
2003	1.2417645826451122
2004	1.489816973336109
2005	1.475801118027437
2006	1.3954116476485487
2007	1.3241097354302598
2008	1.2268495422092096
2009	1.1783779091894149
2010	1.1102699606072814
2011	1.0639030804473673
2012	1.018369553016291
2013	1.0069897280934283
2014	0.9774645852242909