Year	% of total energy use
1971	4.05779232526294
1972	3.9771436306480417
1973	3.95956895831593
1974	3.85334155277896
1975	3.786315246774489
1976	3.62418179196445
1977	3.4941639608897095
1978	3.3048146905008973
1979	3.137008489391213
1980	3.0023605219759877
1981	2.968024996123022
1982	2.882999262304367
1983	2.8208631140116798
1984	2.793203186315963
1985	2.938403691777286
1986	3.157180454861596
1987	3.429132775663383
1988	3.713964931361178
1989	3.7281097102345515
1990	3.4344357902163747
1991	3.460436192343837
1992	3.4788938563560627
1993	3.5426515694474023
1994	3.9906822791891763
1995	4.320354302229993
1996	4.289864214976977
1997	3.8210529951289445
1998	3.840162397584986
1999	3.6314014716423246
2000	3.323889703531428
2001	3.3434256005930454
2002	3.4873103017610347
2003	3.759514972869897
2004	3.918220978028321
2005	3.954661686129915
2006	3.762629162764631
2007	4.661077828152281
2008	4.480984718955136
2009	4.031820434850646
2010	4.5536063303758105
2011	6.0578949237063275
2012	6.083771229553323
2013	8.23145339111011
2014	7.011445517359727