Year	% (national estimate)
1960	71.7
1961	70.8
1962	70
1963	69.1
1964	68.8
1965	69
1966	69
1967	69.3
1968	68.3
1969	68.8
1970	69.4
1971	69.6
1972	71.3
1973	72.9
1974	73.7
1975	72.4
1976	72.9
1977	74.1
1978	74.9
1979	75
1980	74.4
1981	73.7
1982	72.6
1983	72.5
1984	72.8
1985	73
1986	73
1987	72.3
1988	72.4
1989	73
1990	71.8
1991	70.4
1992	70.5
1993	70.2
1994	70.35
1995	70.381
1996	68.998
1997	68.446
1998	68.356
1999	68.027
2000	68.586
2001	67.033
2002	65.489
2003	63.862
2004	63.586
2005	62.947
2006	63.321
2007	61.535
2008	61.015
2009	58.466
2010	56.751
2011	56.605
2012	56.535
2013	56.594
2014	56.411
2015	56.181
2016	56.521
2017	56.649
2018	55.901
2019	56.599
2020	54.597
2021	56.505
2022	56.487
2023	56.579