Year	% of total
1960	85.35506863780358
1961	83.2678270634475
1962	83.5565688230265
1963	79.23134169678929
1964	74.31755145735
1965	72.38370736714413
1966	69.06128576474744
1967	63.27297285889156
1968	57.96296296296296
1969	46.888393622492714
1970	33.64020574648626
1971	26.885699672052233
1972	25.555855369670805
1973	21.679182568016742
1974	26.135557971357
1975	21.4684697927385
1976	22.50281179042081
1977	25.362179692333953
1978	26.565003263513915
1979	28.215008188035835
1980	29.36279218699968
1981	34.87442808335498
1982	37.690583856897035
1983	32.14636873662496
1984	33.79959024026821
1985	26.541531132796532
1986	24.183891289633987
1987	24.162882859755804
1988	25.118916657628482
1989	26.36182843129925
1990	28.246457633870143
1991	27.026381591886047
1992	25.940344489567284
1993	26.714049209339496
1994	27.4540586759367
1995	26.221502802111107
1996	24.230083313370066
1997	20.911624561718963
1998	20.578738958269874
1999	15.027709138017897
2000	19.366218452877145
2001	16.23546770459691
2002	15.641408962304945
2003	13.891648017615873
2004	13.61065996467227
2005	12.242588292944731
2006	10.926163038839096
2007	9.515812082990587
2008	8.656066424990726
2009	6.8558893615125935
2010	6.3463813370562585
2011	6.119262138540005
2012	6.695580794158366
2013	6.278905603427291
2014	6.156471147660205
2015	6.108011732903893