Year	% of total energy use
1971	1.515012886639135
1972	1.9044980879121263
1973	1.9671567904055511
1974	2.3826156614845337
1975	2.4404983826458024
1976	2.6007764286412343
1977	2.7531405029192717
1978	2.5910191169409402
1979	2.819260718439103
1980	2.9442640875861072
1981	3.075379544145038
1982	3.062095332316606
1983	2.7394156403208902
1984	2.773259336953671
1985	3.1247703874098143
1986	3.1814078544543127
1987	2.9880539252592464
1988	2.9758615999245173
1989	3.210684097756744
1990	2.097988437937089
1991	2.1314977509382302
1992	2.106004603388608
1993	2.1338730707798828
1994	1.914323422153974
1995	1.9796888988598715
1996	2.019370753328022
1997	1.9243038947852467
1998	1.661080195137536
1999	1.7916655747796897
2000	2.087669427290336
2001	2.2252602428236763
2002	2.1021214476286003
2003	2.1752032375570773
2004	2.233840662075493
2005	2.2260161589060745
2006	2.2564400818923094
2007	2.2141699611218066
2008	2.3260384713940176
2009	2.3345171094084103
2010	2.450635545637062
2011	2.462372795777273
2012	2.5845789239310446
2013	2.609261233220967
2014	2.394432941005632