Year	% of energy use
1971	10.653464589262203
1972	10.275013367920453
1973	10.857747402048311
1974	10.194345700244986
1975	8.773227899006743
1976	9.772265262085524
1977	9.862892694910983
1978	8.899144449770997
1979	11.066849135834442
1980	10.693318131548878
1981	9.44507645910569
1982	8.55773183972439
1983	7.180890802432978
1984	6.537986905558472
1985	8.285217649992804
1986	7.376943954199991
1987	7.993247414366034
1988	8.221582000143766
1989	9.397630973941316
1990	10.080388287029542
1991	10.16569921141323
1992	12.258193942679622
1993	13.309940437751088
1994	13.75752597650039
1995	14.698304735200164
1996	16.0199733084527
1997	16.8507177625408
1998	18.700373574179846
1999	21.081235920720165
2000	21.304453976059293
2001	20.831403112874835
2002	20.919571489557026
2003	19.930242548338118
2004	21.300208598814244
2005	21.754704910331544
2006	23.124508462957778
2007	24.519103201117638
2008	25.150932541051308
2009	26.468271021055052
2010	27.332681356959878
2011	28.342563070428934
2012	30.17513513837973
2013	30.886160542182115
2014	32.69210781932501