Year	% of total
1960	76.74469687460775
1961	75.26104417670683
1962	73.76074556117939
1963	72.81312247971627
1964	70.12176009644364
1965	67.87678897461569
1966	65.25989424011762
1967	62.239991088061096
1968	61.05774458984305
1969	58.55817506458065
1970	54.082159782584284
1971	51.70376042481647
1972	45.241568840333855
1973	44.86007789191802
1974	42.677662789524
1975	45.79108829693528
1976	45.94703811418949
1977	44.86223289432196
1978	42.861558227479875
1979	43.695696674703186
1980	45.041589122260625
1981	46.6492738840176
1982	44.65547555537728
1983	45.33781286746178
1984	33.56887032303205
1985	41.88466929536136
1986	43.72143101214001
1987	45.3767233087528
1988	43.8190618833043
1989	42.30223718300271
1990	42.415970109037346
1991	41.49855314373882
1992	40.670689175015376
1993	36.50039480500259
1994	34.703591027101744
1995	33.53029430277137
1996	30.29890225094554
1997	28.554341316792065
1998	27.77681084890387
1999	24.931050999310823
2000	25.91497924998114
2001	26.888953680575963
2002	25.409585840107123
2003	26.72862012987013
2004	25.93784481486945
2005	26.520970403255646
2006	28.768523558082858
2007	27.76999225187089
2008	26.419137847242474
2009	24.056409313725492
2010	24.135114884078128
2011	25.82461770397372
2012	31.181433373297935
2013	31.167800291352144
2014	27.602605520067495
2015	22.587994604990385
2016	11.880077331151522