Year	% (national estimate)
1968	55.8
1969	55
1970	55.5
1971	56.1
1972	54.3
1973	52.7
1974	50
1975	47.8
1976	46.1
1977	45.1
1978	44.7
1979	44
1980	43.3
1981	43.6
1982	43.4
1983	44.2
1984	43.7
1985	42.9
1986	43.1
1987	42.6
1988	42.6
1989	43.2
1990	44.08
1991	45.426
1992	46.59
1993	47.173
1994	47.591
1995	47.634
1996	48.266
1997	48.557
1998	48.31
1999	47.239
2000	46.985
2001	46.19
2002	45.39
2003	44.68
2004	43.976
2005	44.519
2006	44.851
2007	44.67
2008	44.434
2009	43.53
2010	43.018
2011	42.623
2012	41.498
2013	42.467
2014	42.956
2015	42.919
2016	44.8
2017	44.594
2018	47.393
2019	49.085
2020	48.551
2021	48.87
2022	48.7
2023	49.9