Year	% (national estimate)
1960	82.07
1970	73.21
1977	61.51
1978	60.34
1979	59.05
1980	58.3
1981	57.78
1982	57.89
1983	56.94
1984	56.96
1985	56.05
1986	54.465
1987	54.469
1988	54.153
1989	51.849
1990	51.572
1991	50.685
1992	49.64
1993	47.958
1994	47.266
1995	44.551
1996	43.971
1997	44.475
1998	45.013
1999	46.359
2000	46.682
2001	47.411
2002	48.566
2003	49.308
2004	49.767
2005	52.536
2006	52.44
2007	52.004
2008	51.539
2009	48.25
2010	44.997
2011	42.568
2012	40.119
2013	39.669
2014	37.635
2015	36.178
2016	34.856
2017	35.025
2018	35.074
2019	35.139
2020	32.306
2021	33.241
2022	34.342
2023	35.111