Year	% of total energy use
1971	3.3566772097922133
1972	3.584003281530215
1973	3.789853781543222
1974	4.2435614299731865
1975	4.537709936886844
1976	4.925170270408294
1977	5.089503641149335
1978	5.241887906483632
1979	5.603474761265987
1980	5.725372599459198
1981	6.072777050991748
1982	6.328915643941216
1983	6.79065979316336
1984	7.385038560760676
1985	7.9225570352272205
1986	8.22437442469868
1987	8.624244340223633
1988	8.743750997334383
1989	8.862396022806191
1990	7.002823576450984
1991	7.083791477009425
1992	7.04023045714035
1993	7.4445581746475815
1994	7.241023463403773
1995	7.76916720241781
1996	7.643836546610499
1997	7.790645448206866
1998	7.558295483182554
1999	7.566920390457661
2000	7.876135799818881
2001	7.735508906517878
2002	7.804752786772342
2003	7.956222585236743
2004	7.786053186841306
2005	7.8439202425619765
2006	7.99087452375226
2007	7.9058840877103185
2008	7.820838989456537
2009	7.999243437447627
2010	7.572069832606521
2011	8.081821212522247
2012	7.574958114001296
2013	7.369460774459075
2014	7.193755516551294
2015	3.8729707321030786