Year	Percent
1961	63.3889
1962	63.76661
1963	63.9229
1964	64.00104
1965	64.21377
1966	64.40479
1967	64.41782
1968	64.99957
1969	64.9822
1970	64.81723
1971	64.83893
1972	64.87367
1973	64.70435
1974	64.81289
1975	64.88669
1976	64.92576
1977	64.94747
1978	64.96918
1979	64.97786
1980	64.96483
1981	64.89537
1982	64.96049
1983	65.03864
1984	65.08639
1985	65.20795
1986	65.2861
1987	65.52488
1988	65.59434
1989	64.34707
1990	64.39503
1991	64.49054
1992	64.45568
1993	64.46875
1994	64.47649
1995	64.47776
1996	64.40397
1997	64.47088
1998	64.23189
1999	64.37718
2000	64.6772
2001	64.42036
2002	64.46252
2003	64.36182
2004	61.43478
2005	61.65754
2006	61.04444
2007	59.28923
2008	59.30405
2009	59.20629
2010	61.53445
2011	60.7464
2012	59.7035
2013	60.44864
2014	60.10953
2015	60.23122
2016	58.76652
2017	58.14499
2018	58.30146
2019	60.09214
2020	56.71506
2021	56.84545