Year	Percent
1961	66.48926
1962	66.49326
1963	66.30317
1964	65.53484
1965	65.41678
1966	64.34031
1967	64.79251
1968	64.34631
1969	65.08264
1970	64.26628
1971	65.39677
1972	65.16467
1973	64.58842
1974	64.18809
1975	63.88928
1976	63.08625
1977	63.23818
1978	63.01523
1979	62.76775
1980	62.54229
1981	62.47948
1982	62.44945
1983	61.65228
1984	61.32468
1985	61.49287
1986	61.28864
1987	61.27062
1988	61.22457
1989	61.47085
1990	61.01233
1991	60.81011
1992	60.6259
1993	60.13335
1994	60.43369
1995	59.50465
1996	60.34559
1997	60.18541
1998	59.98318
1999	59.62278
2000	59.6513
2001	59.21528
2002	58.95119
2003	58.39827
2004	58.23751
2005	58.43435
2006	57.34298
2007	56.10787
2008	56.41941
2009	56.09032
2010	55.0889
2011	54.04097
2012	53.86138
2013	53.44395
2014	53.13368
2015	53.18906
2016	52.57725
2017	52.63871
2018	52.40821
2019	52.45849
2020	52.33168
2021	52.48489