Year	% of total energy use
1971	1.4368840163101277
1972	1.4416117876569328
1973	1.5741091745818203
1974	1.5824079343657744
1975	1.7375044401956714
1976	1.879476698367079
1977	1.8121739797938767
1978	2.0509028422698248
1979	2.0860544103216747
1980	2.285857246337138
1981	2.4210662527227957
1982	2.3873056641803485
1983	2.491956171504212
1984	2.626115543559187
1985	2.5635415907868366
1986	2.6018841427782657
1987	2.5480039483152805
1988	2.7781362892934816
1989	2.8120399037303048
1990	3.200023472491306
1991	3.109215994687979
1992	3.1330038936188664
1993	3.124498076682828
1994	3.0988500013523947
1995	3.0052346351572905
1996	3.1827256864399103
1997	3.099262734912087
1998	3.0727532675206644
1999	2.919252569254908
2000	3.021471474336929
2001	3.0140100296585906
2002	2.9370256649556756
2003	3.0152541642916315
2004	3.03422938332669
2005	3.0756090014387403
2006	3.149916288716725
2007	3.1117116344244
2008	2.9088599813265734
2009	2.810949096542681
2010	3.01223090790369
2011	3.1814156101538558
2012	3.114168288042724
2013	3.213231439784923
2014	3.088260248528448