Year	% of total energy
1971	75.13376091400433
1972	72.96152312531375
1973	70.53958901237156
1974	68.25104300696262
1975	67.12848463891424
1976	65.33496108091718
1977	59.95562277580071
1978	57.20014657802223
1979	55.61235871682242
1980	54.31289608635116
1981	52.676896475739134
1982	52.4579907486617
1983	52.49371841400479
1984	51.41806618348448
1985	50.45884380564091
1986	46.41391034845419
1987	45.657537011010156
1988	45.29829451061966
1989	43.564125492095364
1990	42.56670755578697
1991	41.35066785122958
1992	40.355031266561504
1993	37.36087130708698
1994	37.866581036802984
1995	34.73430866959643
1996	33.762698536735826
1997	33.46178991214621
1998	34.649339371043865
1999	33.44733554819849
2000	31.635647629098912
2001	30.875543978478426
2002	29.856845522364477
2003	29.90136012960285
2004	28.00620735209543
2005	27.3532769526765
2006	27.281389895111346
2007	27.310476413677094
2008	26.975537570664386
2009	25.044091307391703
2010	23.488625339499798
2011	25.075787496059725
2012	25.476168057585657
2013	25.32416188729476
2014	24.79861142403934