Year	% of total energy use
1971	0.1575295689179561
1972	0.19220525733527527
1973	0.17986967582144617
1974	0.20896102633880842
1975	0.16023077205893313
1976	0.27068802924035823
1977	0.2844245553992603
1978	0.3062603925570206
1979	0.3292635576859843
1980	0.3827039222438927
1981	0.4503529898542355
1982	0.5753252693285195
1983	0.6216373492454302
1984	0.6506316684448195
1985	0.7206673267190717
1986	0.8817796302829404
1987	0.8944501148537469
1988	0.8802629642634946
1989	1.105234739708142
1990	0.9408056218095588
1991	0.988226129076786
1992	0.9725934323899824
1993	0.9889608589515496
1994	1.0721859356874874
1995	1.2094932403137086
1996	1.296047395290152
1997	1.3183073389433277
1998	1.4007996552575355
1999	1.569649870550044
2000	1.702709949720729
2001	1.8520518220553364
2002	2.01195802275657
2003	2.144487323212178
2004	2.323785612542467
2005	2.372974203920005
2006	2.5974408669909907
2007	2.713235918024085
2008	2.5950743215623358
2009	2.8476939826979004
2010	3.0028158765142594
2011	3.48110922015826
2012	4.309270290549423
2013	5.255746853573063
2014	5.243247971824756