Year	% of total energy use
1971	4.136795859868818
1972	4.526915517142764
1973	4.895705765182317
1974	5.152562469100428
1975	4.959247263844812
1976	4.927920912221935
1977	5.438958362374734
1978	6.306281184126679
1979	7.094923312225963
1980	6.938373848174366
1981	6.8527508807884665
1982	7.048855095343616
1983	6.890705832571217
1984	7.448258389173794
1985	7.891564414707314
1986	8.385376640533012
1987	8.841995002906017
1988	9.044260283348473
1989	9.811337064995977
1990	7.2140290691277835
1991	7.28468617550786
1992	6.736548522516374
1993	7.513716369814424
1994	8.19123334877329
1995	8.17524590568444
1996	9.014127955926558
1997	7.838845481538459
1998	7.077913961299756
1999	8.454756563964033
2000	8.260166333017168
2001	8.616870313606197
2002	9.109798298438038
2003	9.550539958423306
2004	10.296701615809695
2005	9.785721498800516
2006	9.771520642577144
2007	10.345045162811472
2008	10.381883036080412
2009	9.340378461645994
2010	8.850505811283778
2011	11.005537095222328
2012	10.596873164530125
2013	8.974066211079142
2014	9.203541219221876