Year	% of energy use
1971	-0.7906073111177898
1972	-0.8191557501742655
1973	-1.1141950072199776
1974	-1.9035377360828984
1975	-2.844526186978192
1976	-2.376011711714508
1977	-2.1244891319489043
1978	-2.387013601901283
1979	-3.1154941208229627
1980	-2.9184906736597718
1981	-3.171726128892861
1982	-4.206942351955164
1983	-5.1684127346238995
1984	-6.237454332954979
1985	-7.543744339268377
1986	-6.556212242712507
1987	-4.354344809928944
1988	-2.9684406625307096
1989	-5.991797506697751
1990	-1.1661638515883983
1991	-4.565863899677358
1992	-3.0977563376412123
1993	-0.442131049073803
1994	-1.3699078345255788
1995	-1.9187571146048195
1996	-1.6371052295066895
1997	-0.695494594431339
1998	-0.07124417391966793
1999	2.2553392199073263
2000	0.5484087684974818
2001	-0.6738288796085873
2002	1.5005426389710932
2003	3.0895430476379375
2004	4.894838489547105
2005	6.056192142570065
2006	7.858073702977854
2007	8.421708309604853
2008	8.435545072930362
2009	10.36099569870367
2010	11.44641321802288
2011	11.860123210801216
2012	14.359740378292688
2013	14.756451413436844
2014	15.021800740113905