Year	% of total
1964	50
1965	51.57894736842105
1966	48.71794871794872
1967	39
1968	33.0188679245283
1969	22.115384615384613
1970	25.806451612903224
1971	24.08759124087591
1972	25.503355704697984
1973	26.282051282051285
1974	25.333333333333336
1975	32.278481012658226
1976	28.30188679245283
1977	23.5632183908046
1978	21.85792349726776
1979	14.367816091954023
1980	24.226804123711336
1981	21.21212121212121
1982	27.160493827160497
1983	20.38216560509554
1984	19.736842105263158
1985	15.789473684210526
1986	13.245033112582782
1987	13.422818791946309
1988	8.108108108108107
1989	5.194805194805195
1990	24.955972222222222
1991	20.887974683544304
1992	21.352151898734174
1993	20.418522727272727
1994	19.745384615384616
1995	19.342417582417582
1996	20.55131868131868
1997	20.072000000000003
1998	20.327934782608693
1999	14.897187500000001
2000	19.168409090909087
2001	13.751249999999999
2002	20.893372093023256
2003	19.168409090909087
2004	17.73054945054945
2005	17.32758241758242
2006	16.95494623655914
2007	16.089897959183673
2008	13.667909090909092
2009	12.441607142857142
2010	16.219423076923075
2011	21.551666666666666
2012	19.317232142857144
2013	18.18347107438017
2014	18.335
2015	18.946166666666667
2016	15.908308823529413