Year	Percent
1961	63.07733
1962	62.89653
1963	62.73947
1964	62.29203
1965	62.0948
1966	61.81173
1967	61.41543
1968	60.59178
1969	60.58265
1970	59.34444
1971	59.57821
1972	59.38097
1973	59.28053
1974	59.24765
1975	59.09242
1976	58.4788
1977	58.27608
1978	58.36922
1979	58.13728
1980	57.93274
1981	57.86882
1982	57.79395
1983	57.64602
1984	57.54192
1985	57.42139
1986	57.33555
1987	57.25885
1988	56.30371
1989	56.14099
1990	55.87053
1991	55.67347
1992	55.48975
1993	55.31991
1994	55.16212
1995	55.06222
1996	54.96379
1997	54.86024
1998	54.75139
1999	54.65843
2000	54.43608
2001	54.26423
2002	54.07685
2003	53.90834
2004	53.79871
2005	53.67551
2006	53.5336
2007	53.33892
2008	53.1636
2009	52.99887
2010	52.82792
2011	52.74081
2012	52.67908
2013	52.54923
2014	52.53608
2015	52.46376
2016	52.44755
2017	52.41007
2018	52.34177
2019	52.2707
2020	52.14755
2021	52.14755