Year	Percent
1960	88.18462
1961	89.41451
1962	88.18495
1963	83.78125
1964	81.71429
1965	79.28622
1966	55.35432
1967	46.04016
1968	46.43541
1969	42.17105
1970	43.32403
1971	27.94406
1972	43.00547
1973	49.52747
1974	39.39395
1975	36.50886
1976	30.75327
1977	37.58447
1978	30.33335
1979	34.256
1980	22.43612
1981	24.34777
1982	16.66436
1983	16.25863
1984	15.21385
1985	16.02978
1986	15.83661
1987	14.25375
1988	14.00164
1989	12.62463
1990	12.16165
1991	7.325
1992	9.07709
1993	8.33024
1994	8.26243
1995	8.78063
1996	7.68928
1997	7.0032
1998	8.32299
1999	8.78463
2000	7.82713
2001	8.29887
2002	6.39531
2003	6.34689
2004	5.98401
2005	5.67113
2006	4.84276
2007	4.88999
2008	4.89705
2009	5.50352
2010	4.86218
2011	4.54395
2012	4.89531
2013	5.06436
2014	3.96071
2015	3.7819
2016	4.88462
2017	4.96482
2018	4.24978
2019	4.51811
2020	5.27193
2021	6.11705
2022	6.23857