Year	% (national estimate)
1960	63.4
1961	61.39999999999999
1962	62.1
1963	60.79999999999999
1964	61.1
1965	62.4
1966	63.7
1967	63.900000000000006
1968	63
1969	63.4
1970	61.7
1971	60.7
1972	62.8
1973	65.7
1974	65.3
1975	60.4
1976	61.87667643540326
1977	63.74752844747567
1978	65.51934172094974
1979	66.14732940769508
1980	63.48525427167442
1981	62.335355980865195
1982	58.43287470843931
1983	58.791085361389726
1984	61.784602704635056
1985	62.31289395203526
1986	62.771629065468424
1987	63.13356266176786
1988	64.09090221194543
1989	64.70895091108208
1990	63.41208539019873
1991	59.98662916717732
1992	59.183978745315244
1993	59.45182828690621
1994	60.388520380266044
1995	60.839790306360754
1996	59.5417347353188
1997	59.56564178420089
1998	60.038335895720984
1999	60.47318153574383
2000	61.426032957365905
2001	59.09563550636342
2002	57.114280203175745
2003	55.55572269281721
2004	55.729909416672584
2005	55.29736069773604
2006	56.4179201672629
2007	54.952522501638455
2008	52.95824419223219
2009	47.435946797323155
2010	45.80501503031939
2011	46.869396771669614
2012	47.30400455914418
2013	47.75195416784594
2014	48.88221581624999
2015	49.644388436771926
2016	50.53076539683988
2017	51.399696240122665
2018	51.23543967413028
2019	51.889014075759746
2020	46.70600677991798
2021	50.96517964548863
2022	52.0821686443914
2023	52.16880649524994