Year	% of total energy
1960	1.6048302821506433
1961	1.5583504513560098
1962	1.499144088469032
1963	1.4948831934132636
1964	1.4615896873542842
1965	1.9938073919968533
1966	1.9396891720846252
1967	1.9333971461472064
1968	1.8049294784361851
1969	1.9992859283558957
1970	1.5530315639145886
1971	1.617650197760903
1972	1.6850300036773307
1973	1.5240097819137899
1974	1.4546662726914177
1975	1.3468362556506366
1976	1.2671786497055886
1977	1.1969918491242117
1978	1.0861502850148352
1979	0.9621429020425585
1980	0.9712623061313229
1981	1.172432361118393
1982	1.1445011024616059
1983	1.1618127315941527
1984	1.2554109164737175
1985	1.3047899160664356
1986	1.4688729627425472
1987	1.2571751793701682
1988	1.2144581377071677
1989	1.163708055627083
1990	1.7957674901328584
1991	2.0601376083768446
1992	2.3959003371339964
1993	3.4682733275366266
1994	3.613742207610451
1995	3.580445193161956
1996	4.03566272388681
1997	4.400430088500963
1998	4.5583806669583105
1999	4.688508500549466
2000	4.790052653639342
2001	4.734257915636334
2002	4.867801137409063
2003	5.086428478729772
2004	5.24538312366896
2005	5.276372404500382
2006	5.213390070199568
2007	5.382445143627229
2008	5.897668220624874
2009	6.833716005354901
2010	7.3535237221702205
2011	7.471973738046656
2012	8.023027212979557
2013	8.276438131334345
2014	8.201238177680695
2015	7.089814099830291