Year	% of total energy use
1971	4.751568455092844
1972	5.575463074691721
1973	5.6604998820067465
1974	6.485220843084397
1975	7.1979737584901144
1976	7.0222410852219195
1977	7.155715926194165
1978	7.188915356691069
1979	6.982397496780933
1980	7.141577539288877
1981	7.279013551905214
1982	8.682226942216266
1983	9.055565699836933
1984	8.931366687027774
1985	9.934807327225641
1986	10.161029617976128
1987	10.670895114174952
1988	9.2324089879526
1989	6.914796583883141
1990	4.620632570164722
1991	6.697138208542127
1992	8.031184231022257
1993	8.201461157268
1994	7.330024785388485
1995	7.452478303473696
1996	6.25053412046929
1997	6.312652438977484
1998	5.074304539144379
1999	4.22844137480227
2000	5.801978066776317
2001	6.79874398484083
2002	7.0243815921204185
2003	6.853466537144144
2004	6.315504827622806
2005	7.393830499766922
2006	7.79474617098192
2007	5.890076615148719
2008	6.157827882728986
2009	6.577652879488934
2010	5.567666160112288
2011	4.815478303642048
2012	4.291804322776555
2013	4.08270933094002
2014	5.6453850608006775
2015	5.722212159206048