Year	% of total energy
1971	15.035781214665652
1972	14.747102700486549
1973	13.726774846648466
1974	13.081154960065602
1975	12.363982377807828
1976	11.421097265939453
1977	10.712397029545194
1978	9.53177305891232
1979	8.225527381183289
1980	7.516092895562653
1981	6.696784603065706
1982	6.182946573051066
1983	5.938383738697504
1984	5.86052146756304
1985	5.697053847386587
1986	5.5644228530721564
1987	5.247116874254898
1988	4.919107184365725
1989	4.737887437268102
1990	3.098762543935863
1991	3.0892890192060487
1992	2.8451107677881207
1993	2.708441632221614
1994	2.7857987320664344
1995	2.736548600870044
1996	2.7481902937285234
1997	2.709771921567698
1998	2.732889262957978
1999	2.7623587770494464
2000	2.7365248878189585
2001	2.615183264896976
2002	2.5503505209358286
2003	2.5631370676865526
2004	2.718790289176289
2005	2.577663909829899
2006	2.4784723530847543
2007	2.251218881570453
2008	2.0611417294540932
2009	1.9804162253420763
2010	1.840428860764695
2011	1.8370934870505302
2012	1.5101252749030107
2013	1.535386274418142
2014	1.5031051321972944