Year	% of total energy use
1971	0.2998081768375915
1972	0.4390195053890728
1973	0.4985338039641597
1974	0.5361120590282163
1975	0.5770195785691987
1976	0.6488164557317605
1977	0.5917919572123249
1978	0.5992961626505384
1979	0.6479679928884342
1980	0.5880605490055438
1981	0.599732065845736
1982	0.6148501737501828
1983	0.6164036156169486
1984	0.658013664049511
1985	0.669387786138935
1986	0.7807422194121759
1987	0.8177131340822567
1988	0.7636175915545759
1989	0.7665345953883438
1990	0.6441229824332312
1991	0.6296889071293013
1992	0.6887563511842322
1993	0.6756153641447604
1994	0.5765001590772798
1995	0.5027704277232269
1996	0.5093349981590974
1997	0.4519951251598769
1998	0.48153125793734053
1999	0.621517615368685
2000	0.6411105691472411
2001	0.5096492417550439
2002	0.5262041128049348
2003	0.4894026343829761
2004	0.46613313227745895
2005	0.5722352959241273
2006	0.5601122243492529
2007	0.6111374109984689
2008	0.6187836447278666
2009	1.3199022291497042
2010	2.5650840668086605
2011	2.6418494389021445
2012	3.2061931750057413
2013	3.752617676554906
2014	4.365390489001161