Year	% of total energy
1971	3.2395621327967827
1972	3.2017359494864426
1973	2.8358017676327205
1974	2.652889333280247
1975	2.469905234351985
1976	2.271265249029046
1977	2.141366714948862
1978	1.9391466695382995
1979	1.6889995947598355
1980	1.565522587480486
1981	1.4117777077575902
1982	1.2919596868311303
1983	1.2812331905330532
1984	1.2551870651378438
1985	1.242865731111164
1986	1.2217751639794106
1987	1.1524569763818693
1988	1.1123204336162527
1989	1.019330194569507
1990	1.000508266365813
1991	1.0070793794284114
1992	0.9465011741998619
1993	0.9060849739809319
1994	0.8831553761579561
1995	0.8542906607594445
1996	0.8525812382477073
1997	0.8193746582357703
1998	0.8147752640566187
1999	0.7972707901592594
2000	0.7987556465813017
2001	0.7555389059209677
2002	0.7373433051337258
2003	0.7311017451802351
2004	0.8817415926344438
2005	0.8909113848829989
2006	0.8229893326739065
2007	0.7790648860191804
2008	0.7099962355271521
2009	0.6792317101578765
2010	0.6204429701806116
2011	0.5955502905890917
2012	0.5538773413339484
2013	0.5552578526163345
2014	0.5301136188905604
2015	0.03773378548007887