Year	% (national estimate)
1960	56.1
1961	55.4
1962	55.5
1963	55.4
1964	55.7
1965	56.2
1966	56.9
1967	57.3
1968	57.5
1969	58
1970	57.4
1971	56.6
1972	57
1973	57.8
1974	57.8
1975	56.1
1976	56.8
1977	57.9
1978	59.3
1979	59.9
1980	59.2
1981	59
1982	57.8
1983	57.9
1984	59.5
1985	60.1
1986	60.7
1987	61.5
1988	62.3
1989	63
1990	62.8
1991	61.7
1992	61.5
1993	61.7
1994	62.579
1995	62.948
1996	63.223
1997	63.844
1998	64.06
1999	64.253
2000	64.396
2001	63.663
2002	62.732
2003	62.277
2004	62.345
2005	62.689
2006	63.12
2007	62.987
2008	62.177
2009	59.32
2010	58.472
2011	58.372
2012	58.561
2013	58.584
2014	59.007
2015	59.343
2016	59.729
2017	60.114
2018	60.422
2019	60.784
2020	56.772
2021	58.361
2022	59.965
2023	60.326