Year	% of total energy
1960	3.3244324853350795
1961	3.2296440098696073
1962	3.099452365792944
1963	2.989211696544543
1964	2.893144420524741
1965	2.751121087816824
1966	2.674869582306985
1967	2.547719843928001
1968	2.6025862269091165
1969	2.552948121606035
1970	2.519797152808904
1971	2.4722608964630455
1972	2.4438660754738115
1973	2.398277476642759
1974	2.4549401128463377
1975	2.362496364873433
1976	2.496154279990295
1977	2.5730031265818853
1978	2.7631610165227047
1979	2.9014943786050447
1980	3.1120738576643734
1981	3.2023709107971507
1982	3.3790588487664905
1983	3.6046108240108645
1984	3.818867394521662
1985	3.74048578768889
1986	3.830812952910107
1987	4.006395577123104
1988	3.817577154809593
1989	3.5838821200265296
1990	1.7677542156727624
1991	1.8470873740570404
1992	2.071564921413724
1993	1.7223931247305158
1994	1.7377448288173103
1995	1.934670075403208
1996	1.833916646657671
1997	1.7479505448153245
1998	1.889582049546962
1999	2.460785003126763
2000	2.446506480697427
2001	2.181304316293996
2002	2.0411512576217477
2003	2.2808708685390493
2004	2.4110666086844077
2005	2.5543335435578602
2006	2.7554403886447623
2007	2.786796321256418
2008	2.991893010983399
2009	3.077161970597219
2010	3.307651419267231
2011	3.3920780526083925
2012	3.6406850440870113
2013	3.75644806758848
2014	3.7414535457244273
2015	3.6745110272254866