Year	% (national estimate)
1960	68.037
1961	68.121
1962	67.446
1963	66.23
1964	65.361
1965	64.91
1966	64.949
1967	65.105
1968	65.147
1969	64.765
1970	64.604
1971	64.181
1972	63.519
1973	63.838
1974	62.786
1975	61.862
1976	61.721
1977	61.893
1978	61.976
1979	62.092
1980	61.979
1981	61.894
1982	61.847
1983	62.099
1984	61.688
1985	61.352
1986	61.051
1987	60.813
1988	61.032
1989	61.44
1990	62.064
1991	62.48
1992	62.608
1993	62.189
1994	61.771
1995	61.421
1996	61.34
1997	61.525
1998	60.746
1999	59.907
2000	59.478
2001	58.881
2002	57.936
2003	57.575
2004	57.559
2005	57.731
2006	57.89
2007	58.047
2008	57.748
2009	56.83
2010	56.539
2011	56.553
2012	56.44
2013	56.853
2014	57.31
2015	57.485
2016	58.107
2017	58.738
2018	59.931
2019	60.551
2020	60.207
2021	60.359
2022	60.908
2023	61.242