Year	% of total energy use
1971	0.7262613276590045
1972	1.0573462846747481
1973	1.0566135165023365
1974	1.365164294598315
1975	1.417020843803549
1976	1.5287698112562575
1977	1.6638939282375487
1978	1.5581050530327742
1979	1.560023300644258
1980	1.3932539932330728
1981	1.3940370471366124
1982	1.3171277494877198
1983	1.2684083899525556
1984	1.802935132287333
1985	2.057477559891135
1986	2.700694849443995
1987	2.1050495229695616
1988	2.7998506373858527
1989	2.943617672227536
1990	2.0813103099055885
1991	2.186884190338204
1992	2.2339922270214347
1993	1.8365328656928965
1994	2.100293544564267
1995	2.224633504827058
1996	2.292018160528401
1997	2.349575295569546
1998	2.4516766454377836
1999	2.3215225455021855
2000	2.4596672334949825
2001	2.2881116722955346
2002	2.509645381898845
2003	2.604896344092844
2004	2.593331593608336
2005	2.408645873031253
2006	2.4033663743672498
2007	2.393256156558456
2008	2.4318566396161256
2009	2.4202010493207733
2010	2.504935139990602
2011	2.624055058550319
2012	2.5581470210747894
2013	2.763342867240561
2014	2.5848310920705195