Year	% (national estimate)
1968	53.4
1969	52.8
1970	53.4
1971	52.9
1972	50.7
1973	50.1
1974	46.9
1975	45.6
1976	44
1977	44.4
1978	44.5
1979	44.3
1980	43.9
1981	43.8
1982	43.5
1983	44.4
1984	44.2
1985	43.2
1986	43.7
1987	43
1988	43.1
1989	44
1990	44.794
1991	45.784
1992	46.482
1993	46.674
1994	47.123
1995	47.241
1996	47.571
1997	47.68
1998	47.79
1999	46.74
2000	46.811
2001	46.365
2002	45.126
2003	44.355
2004	44.349
2005	44.974
2006	45.381
2007	44.679
2008	44.792
2009	44.86
2010	43.886
2011	43.649
2012	42
2013	43.462
2014	43.601
2015	43.096
2016	44.939
2017	45.21
2018	48.151
2019	50.214
2020	49.175
2021	49.742
2022	49.8
2023	51.1