Year	% of total energy use
1971	1.0701543769335362
1972	1.3961577894397739
1973	1.4582361674363826
1974	1.7862410014162786
1975	1.8771787682696714
1976	2.0519064161339187
1977	2.220236615683565
1978	2.1191716372254494
1979	2.289129428221271
1980	2.4424199670006526
1981	2.5019627391089774
1982	2.4641996154200525
1983	2.1898414367969927
1984	2.244007712581832
1985	2.479477592090136
1986	2.451984044344683
1987	2.3097462347823106
1988	2.274313999555156
1989	2.480759304487574
1990	2.7933615071849305
1991	2.7887959858210087
1992	2.7927062656645028
1993	2.712530494716272
1994	2.635346286114606
1995	2.526220109370754
1996	2.502129463695361
1997	2.27613121205973
1998	2.0566017261918432
1999	2.2133102578599204
2000	2.405003169861299
2001	2.430200039267486
2002	2.317124711777937
2003	2.4130796565422217
2004	2.432915171098638
2005	2.4087412473702154
2006	2.417910950947212
2007	2.3486632186412546
2008	2.3628393859717045
2009	2.3673770651581116
2010	2.5165488168537435
2011	2.6610505537439972
2012	2.848355638804996
2013	2.957033091289765
2014	2.8400824077555415