Year	% of total energy use
1971	0.6597493515552489
1972	0.7108582888879561
1973	0.766039774688481
1974	0.8448297150214831
1975	0.8005996429263531
1976	0.7844134001035502
1977	0.7517087519204556
1978	0.6499894164044707
1979	0.7182719016199751
1980	0.837107505567271
1981	0.9498476818238843
1982	1.0453750954976553
1983	1.1670133544129941
1984	1.1055582878108576
1985	1.1490604193867877
1986	1.1353534300267025
1987	1.1425491135706367
1988	1.1828999234001447
1989	1.2569298440268348
1990	0.9187117386321041
1991	0.9893552434020514
1992	1.0140209832707079
1993	1.1403409999969498
1994	1.63850291953844
1995	1.7017238794778364
1996	1.716526586444072
1997	1.773303683416473
1998	1.864066575646327
1999	1.8653579601753345
2000	1.9971428488641794
2001	2.2988972634625773
2002	2.420432289076869
2003	2.5210476561276143
2004	2.6789060609014106
2005	2.7339176928011013
2006	2.738780474800132
2007	2.9245298008193203
2008	3.3841025297286396
2009	3.4683171611763655
2010	3.5093415355574864
2011	3.5224346333340226
2012	4.09182975952194
2013	4.534146551219118
2014	5.107017150209008