Year	% of total energy use
1971	3.237321980604529
1972	3.4542457542357425
1973	3.6788742916800414
1974	4.159021653273265
1975	4.430225459189689
1976	4.8135062450260255
1977	4.9434042475069795
1978	5.134387294190047
1979	5.510887472750239
1980	5.638852072430649
1981	6.032772752635183
1982	6.233457777180927
1983	6.6655294735551
1984	7.260922240682091
1985	7.780153009138422
1986	8.072193556451946
1987	8.364193900127585
1988	8.465009340203922
1989	8.683564149323269
1990	6.92877252333078
1991	6.9176603854470455
1992	6.904427464865757
1993	7.309308500857512
1994	7.177020564589829
1995	7.725394912182563
1996	7.664663207984384
1997	7.770096225421448
1998	7.649589779520241
1999	7.660686470996467
2000	7.910385007314913
2001	7.787304399282197
2002	7.945713150503157
2003	8.089658447643751
2004	7.8772057482509545
2005	7.879042306396666
2006	8.11272330282797
2007	8.038415756999
2008	8.016632593542793
2009	8.17649455577706
2010	7.819295646277979
2011	8.3657963999222
2012	7.874214105959737
2013	7.500913532064948
2014	7.29200191805837
2015	3.5172107358416227