Year	% of total energy
1971	78.35560023553131
1972	79.03731168560275
1973	75.34050355236879
1974	74.23211748824168
1975	74.75773530806924
1976	71.98072507516558
1977	72.19395723636428
1978	71.1915686747869
1979	69.93813884268937
1980	67.25723013182827
1981	66.66050871018454
1982	64.54319477435335
1983	66.00050133824969
1984	64.26465637361713
1985	62.03460938672942
1986	60.54994096016667
1987	55.70291873285866
1988	55.311354262691495
1989	54.27343060196827
1990	53.12513591421574
1991	53.89906760777482
1992	51.85304882976517
1993	49.47866121901975
1994	48.35393829978304
1995	44.63748320298443
1996	42.75038630865241
1997	42.308568648798634
1998	41.199542890211845
1999	41.548113741003846
2000	40.94477241550913
2001	38.14212549489574
2002	37.93528126016476
2003	36.62503144066376
2004	36.54252654898399
2005	35.71434870117002
2006	33.777152640816944
2007	32.72373925615474
2008	31.529541596888933
2009	30.303336515327615
2010	28.299195876939393
2011	27.60178495356363
2012	26.619850063519934
2013	26.38645940704574
2014	25.57640341523127