Year	% of total energy use
1971	0.4310537446359836
1972	0.38281894830442526
1973	0.4311444348601803
1974	0.4555945268683823
1975	0.4983685348982153
1976	0.7084738680118198
1977	1.7733845969640936
1978	3.8161739020955197
1979	3.9817684384108216
1980	5.869671264707986
1981	7.6069709569981105
1982	5.591921246685314
1983	4.223863159446921
1984	7.942949821099157
1985	10.63534884436569
1986	11.371025635526129
1987	10.31399636077976
1988	11.983825884288283
1989	12.621468325878633
1990	9.84876636451809
1991	8.488508301035031
1992	7.027016705303936
1993	8.345828820923314
1994	8.309409062731827
1995	8.490094782529006
1996	9.441561996070224
1997	9.171967588168908
1998	5.790814475276662
1999	8.276140520356682
2000	8.899435149204146
2001	5.665397944072651
2002	8.588560129840928
2003	7.078244227123169
2004	9.92142078150483
2005	9.016566409650476
2006	8.14563333747608
2007	8.581202779334394
2008	9.503467179202882
2009	8.247811178040791
2010	8.43798584148975
2011	7.594127994324507
2012	9.55207106504567
2013	9.349303859263253
2014	8.856580595498267