Year	% of energy use
1971	-3.980820509403505
1972	-5.482409762107191
1973	-7.268683198538913
1974	-7.94103031861715
1975	-7.450913999005681
1976	-8.866858184205666
1977	-9.203951732631953
1978	-8.552701068084003
1979	-9.047835578023008
1980	-8.796310846539233
1981	-8.866948248680602
1982	-8.143252951465362
1983	-9.291091985754148
1984	-12.533039338502984
1985	-12.4852357041451
1986	-12.03516656365695
1987	-9.722283436477914
1988	-8.261259627831457
1989	-10.993495187718867
1990	-6.668202057706991
1991	-10.222099084298419
1992	-8.626655806154387
1993	-5.6470396988598495
1994	-6.936309665808453
1995	-6.402018703365728
1996	-6.220916185662942
1997	-5.419967622607906
1998	-5.922948615088286
1999	-4.142369645707333
2000	-4.421545211078328
2001	-5.017822870654824
2002	-3.0277321301418683
2003	-1.5137998758706248
2004	0.03709222738114671
2005	0.5889950844108609
2006	1.2855853104878627
2007	2.221774212282523
2008	2.4567329346843834
2009	3.803615911936543
2010	4.80523711312253
2011	3.9586117346874463
2012	6.270473323834408
2013	6.6190618092159
2014	7.700382741098966