Year	% (national estimate)
1960	63.4
1961	61.4
1962	62.1
1963	60.8
1964	61.1
1965	62.4
1966	63.7
1967	63.9
1968	63
1969	63.4
1970	61.7
1971	60.7
1972	62.8
1973	65.7
1974	65.3
1975	60.4
1976	62.1
1977	64.2
1978	66.1
1979	66.5
1980	63.5
1981	62.2
1982	58.7
1983	59.2
1984	62.3
1985	62.7
1986	63
1987	63.2
1988	64.1
1989	64.7
1990	63.5
1991	60.3
1992	59.7
1993	60.1
1994	61.065
1995	61.543
1996	60.22
1997	60.297
1998	60.794
1999	61.022
2000	61.922
2001	59.373
2002	57.093
2003	55.333
2004	55.549
2005	55.15
2006	56.206
2007	54.425
2008	52.254
2009	46.698
2010	44.932
2011	45.994
2012	46.558
2013	46.943
2014	48.209
2015	49.003
2016	50.052
2017	50.802
2018	50.58
2019	51.276
2020	46.407
2021	50.559
2022	51.537
2023	51.624