Year	% of energy use
1971	23.383462773402123
1972	25.46515545612592
1973	28.119123247838928
1974	32.59159019895543
1975	34.17672187663944
1976	37.810182920395576
1977	41.62698467154286
1978	43.88541793172935
1979	44.091404042403845
1980	42.89534721900079
1981	43.67019755135726
1982	41.721648307051495
1983	45.75274796024676
1984	46.877280307068006
1985	43.493337374715274
1986	47.13398262179112
1987	47.87591001459039
1988	53.307496768875275
1989	54.18111054418597
1990	55.45939667514038
1991	58.45552282768778
1992	59.048043615095935
1993	62.67848681040026
1994	65.87286187851343
1995	63.29540094867176
1996	65.3939128327291
1997	63.78778712717006
1998	65.49165738433449
1999	75.80206568401093
2000	73.86310096486956
2001	73.52793677367782
2002	75.4207268959092
2003	75.8414549014986
2004	75.46381544971133
2005	77.3982019457829
2006	79.50369519306871
2007	80.32561528238139
2008	79.38891753767228
2009	81.04683310487981
2010	81.65622435446316
2011	82.43963256582438
2012	83.15317008275878
2013	83.7810984991436
2014	84.5422889477177