Year	Percent
1961	69.12335
1962	69.06129
1963	69.98448
1964	69.75175
1965	67.32351
1966	70.51978
1967	70.69822
1968	70.93095
1969	70.93871
1970	71.02405
1971	71.02405
1972	71.06284
1973	70.93095
1974	70.91544
1975	70.73701
1976	70.71373
1977	70.69046
1978	71.17921
1979	71.22576
1980	71.218
1981	71.41971
1982	71.41971
1983	71.23351
1984	71.44298
1985	71.24903
1986	71.218
1987	71.19472
1988	71.21024
1989	71.48953
1990	71.54383
1991	71.09387
1992	71.11715
1993	71.06284
1994	71.14042
1995	71.09387
1996	71.15593
1997	69.7052
1998	68.13033
1999	67.26144
2000	66.16757
2001	65.4616
2002	64.72459
2003	64.01862
2004	62.68425
2005	62.1024
2006	61.00078
2007	60.1474
2008	59.40264
2009	58.65012
2010	58.0993
2011	57.37781
2012	56.50116
2013	55.49263
2014	48.10706
2015	48.09154
2016	47.60279
2017	46.96308
2018	46.11086
2019	45.51736
2020	45.51736
2021	45.51736