Year	% of total energy use
1971	3.1346432461554405
1972	3.363462355925226
1973	3.5530595977209236
1974	3.989834971718345
1975	4.294124003166424
1976	4.657118664990309
1977	4.809665209698905
1978	4.965357121706106
1979	5.3178170227872945
1980	5.445335485333687
1981	5.7798453327207335
1982	6.019821279591408
1983	6.441145451923248
1984	7.0488322215458625
1985	7.594087105093108
1986	7.8936946180040914
1987	8.282294728683214
1988	8.390029959687771
1989	8.479451690774757
1990	6.7379946876589845
1991	6.867642066273946
1992	6.856791119084591
1993	7.28342346080047
1994	7.087253850984004
1995	7.605927739317082
1996	7.47633954850165
1997	7.62227281776508
1998	7.409677386208868
1999	7.414283089935795
2000	7.707780688293193
2001	7.5757769772000065
2002	7.657448632771318
2003	7.81059529146586
2004	7.652025609576072
2005	7.720658899321472
2006	7.8712454869996344
2007	7.795435774210247
2008	7.708720701582541
2009	7.876795275440305
2010	7.452712657752325
2011	7.964444612900798
2012	7.466039133857662
2013	7.269651632551207
2014	7.087965633779121
2015	3.8729707321030786