Year	% of total energy
1971	4.9042870959906955
1972	4.757490118016689
1973	4.263710233876314
1974	3.799282866714223
1975	3.555688470657683
1976	3.2173341225228174
1977	3.0632801007717285
1978	2.898011792635993
1979	2.607824099114628
1980	2.56743679915154
1981	2.3993052725808974
1982	2.1810385442223104
1983	2.2039767557374734
1984	2.066622013230181
1985	2.0268225238839137
1986	2.0025252675601193
1987	1.9617503773255256
1988	1.957943169801154
1989	1.7673478319652383
1990	1.6122024927734975
1991	1.6434748944566664
1992	1.5631152454191932
1993	1.4969882295863313
1994	1.459033859294778
1995	1.4010766719725924
1996	1.431782682204483
1997	1.3336882634416447
1998	1.3608324343897105
1999	1.3190077622927863
2000	1.3385533205179618
2001	1.2668753522307687
2002	1.2538624341535147
2003	1.2417645826451122
2004	1.4898169733361093
2005	1.4758011180274375
2006	1.3954116476485485
2007	1.3241097354302596
2008	1.2268495422092098
2009	1.1783779091894149
2010	1.1102699606072812
2011	1.0639030804473675
2012	1.018369553016291
2013	1.0069897280934283
2014	0.9774645852242908