Year	% (national estimate)
1960	27.63
1970	38.09
1977	50.82
1978	50.24
1979	49.42
1980	47.91
1981	47.18
1982	46.61
1983	46.11
1984	45.6
1985	44
1986	38.778
1987	44.355
1988	45.157
1989	43.329
1990	42.557
1991	40.087
1992	39.431
1993	38.16
1994	39.211
1995	38.579
1996	37.152
1997	37.053
1998	37.074
1999	37.652
2000	39.446
2001	37.192
2002	38.483
2003	39.178
2004	39.788
2005	43.045
2006	44.143
2007	43.549
2008	43.72
2009	41.793
2010	40.394
2011	39.166
2012	37.757
2013	35.961
2014	34.069
2015	33.19
2016	31.254
2017	31.6
2018	30.84
2019	30.761
2020	27.476
2021	29.77
2022	30.994
2023	30.942