Year	% (national estimate)
1968	58.3
1969	57.2
1970	57.7
1971	59.1
1972	57.8
1973	55.5
1974	53
1975	50.2
1976	48.3
1977	45.9
1978	44.9
1979	43.9
1980	42.9
1981	43.3
1982	43.3
1983	43.9
1984	43.3
1985	42.5
1986	42.7
1987	42.2
1988	42
1989	42.4
1990	43.402
1991	45.086
1992	46.694
1993	47.648
1994	48.037
1995	48.008
1996	48.927
1997	49.392
1998	48.805
1999	47.714
2000	47.152
2001	46.022
2002	45.643
2003	44.992
2004	43.617
2005	44.08
2006	44.34
2007	44.661
2008	44.09
2009	42.25
2010	42.188
2011	41.638
2012	41.016
2013	41.511
2014	42.34
2015	42.751
2016	44.667
2017	44.01
2018	46.678
2019	48.023
2020	47.957
2021	48.046
2022	47.7
2023	48.5