Year	% (national estimate)
1960	78.9
1961	77.6
1962	77.7
1963	77.1
1964	77.3
1965	77.5
1966	77.9
1967	78
1968	77.8
1969	77.6
1970	76.2
1971	74.9
1972	75
1973	75.5
1974	74.9
1975	71.7
1976	72
1977	72.8
1978	73.8
1979	73.8
1980	72
1981	71.3
1982	69
1983	68.8
1984	70.7
1985	70.9
1986	71
1987	71.5
1988	72
1989	72.5
1990	72
1991	70.4
1992	69.8
1993	70
1994	70.485
1995	70.823
1996	70.954
1997	71.379
1998	71.582
1999	71.645
2000	71.893
2001	70.87
2002	69.707
2003	68.898
2004	69.19
2005	69.603
2006	70.071
2007	69.763
2008	68.504
2009	64.546
2010	63.694
2011	63.869
2012	64.388
2013	64.403
2014	64.88
2015	65.343
2016	65.771
2017	66.033
2018	66.33
2019	66.58
2020	62.388
2021	63.903
2022	65.467
2023	65.529