Year	% of total energy use
1971	0.6233432749836237
1972	0.6556659418513087
1973	0.7346500241723766
1974	0.8127973472993733
1975	0.7863690753502995
1976	0.7792808342847612
1977	0.7307642584169879
1978	0.6420180590201754
1979	0.7864107425100156
1980	1.040561631712422
1981	1.23652180081236
1982	1.4144212958778937
1983	1.5874475398538375
1984	1.603604424464879
1985	1.6625142502820716
1986	1.628989378527598
1987	1.6700776373350557
1988	1.7677796477381238
1989	1.8832167686805068
1990	0.9486793243307229
1991	0.9992795904042874
1992	1.0188639867361762
1993	1.1051573839016071
1994	1.5160685870882042
1995	1.5671740520682176
1996	1.5767299077946535
1997	1.5819009788521083
1998	1.6763823631096244
1999	1.7043059546465729
2000	1.818680545507088
2001	2.0693985377833926
2002	2.1344425470174806
2003	2.2262410898487044
2004	2.355071266117289
2005	2.409455728829383
2006	2.4565926090184234
2007	2.6252587384153734
2008	3.0173890473555027
2009	3.1047041091797842
2010	3.1371657881191175
2011	3.224843703844409
2012	3.7327884851585833
2013	4.09693912277525
2014	4.538817984577552