Year	% of total energy use
1971	0.7562371359120086
1972	0.7831025605133765
1973	0.8562483615604296
1974	0.9295842529531992
1975	0.8955016172655226
1976	0.8854096623308126
1977	0.8309550387537816
1978	0.738078052417081
1979	0.8748963701139505
1980	1.1185057081400531
1981	1.3071012017909678
1982	1.4751265832370393
1983	1.6384058785017603
1984	1.6514685282280848
1985	1.714279893645452
1986	1.687646498778019
1987	1.7322447838373694
1988	1.8343697328272017
1989	1.944445752879865
1990	1.0219557139088118
1991	1.0691521970601623
1992	1.0779593488252808
1993	1.1560670151081995
1994	1.561486252271634
1995	1.6114658490018905
1996	1.6139044568606977
1997	1.6108417457907875
1998	1.702481855728804
1999	1.7286018673771937
2000	1.838218094325562
2001	2.0858902742020704
2002	2.150269796110772
2003	2.242690611033702
2004	2.3703561514209186
2005	2.4238885792966016
2006	2.4680251586795987
2007	2.6394059872356124
2008	3.0282522298799996
2009	3.111108873306249
2010	3.1456410780339032
2011	3.236714606634671
2012	3.74244476076316
2013	4.1094349529494565
2014	4.5470170260409475