Year	% (national estimate)
1960	50.1
1961	49
1962	49.5
1963	48.5
1964	49
1965	50.2
1966	52.2
1967	52.7
1968	52.7
1969	54
1970	53.2
1971	52.3
1972	54.3
1973	57
1974	57.2
1975	54.2
1976	55.7
1977	57.6
1978	59.8
1979	60.6
1980	58.6
1981	57.6
1982	55.3
1983	55.6
1984	58.3
1985	59
1986	59.5
1987	60.1
1988	60.8
1989	61.2
1990	59.8
1991	57.2
1992	56.7
1993	57.2
1994	58.203
1995	58.341
1996	57.748
1997	58.192
1998	58.994
1999	58.997
2000	59.661
2001	57.714
2002	55.693
2003	53.907
2004	53.901
2005	53.907
2006	54.248
2007	53.127
2008	51.226
2009	46.851
2010	45.002
2011	45.454
2012	45.984
2013	46.492
2014	47.638
2015	48.604
2016	49.413
2017	50.343
2018	50.46
2019	51.187
2020	45.864
2021	50.117
2022	51.053
2023	51.786