Year	% of energy use
1971	15.939317031004403
1972	16.835634723025187
1973	18.34799124874661
1974	18.569896339807972
1975	18.531320937419785
1976	19.504698463756263
1977	17.5929426733977
1978	14.041913310038154
1979	9.9593176265494
1980	2.2157498917390885
1981	-6.231519773925403
1982	-13.145897873848451
1983	-17.222271445255952
1984	-18.426840246462483
1985	-17.667856577614202
1986	-14.640748147170884
1987	-13.252053577432934
1988	-13.311703066671335
1989	-12.869089742816048
1990	-14.503921943821464
1991	-14.257666038415461
1992	-14.144161073293317
1993	-14.56012377052295
1994	-13.166264963225311
1995	-14.892298777109813
1996	-16.981663180088066
1997	-17.768767986131362
1998	-17.837997862088795
1999	-18.23251461076147
2000	-19.457257624188625
2001	-20.907716690254222
2002	-22.616241891905787
2003	-25.48712980431837
2004	-23.83032217471891
2005	-23.064135675774313
2006	-22.332610579964825
2007	-19.29577271067368
2008	-15.817578974286663
2009	-17.28117732446784
2010	-14.867823438920432
2011	-15.639039197803807
2012	-13.076599896953105
2013	-10.254601829365578
2014	-10.297144785689653
2015	-4.666485312736533