Year	% (national estimate)
1960	38.2
1961	37.9
1962	38.3
1963	37.6
1964	38.2
1965	39.2
1966	41.9
1967	43.00000000000001
1968	43.79999999999999
1969	45.79999999999999
1970	45.7
1971	44.7
1972	46.4
1973	48.8
1974	49.599999999999994
1975	48.3
1976	49.7805522525889
1977	51.23679630409555
1978	53.655554536270635
1979	54.78449873434626
1980	54.12557964582885
1981	53.703302864612084
1982	52.19697968007737
1983	52.37519331069832
1984	54.46034826048629
1985	55.521416445400135
1986	56.224149139034715
1987	57.33097323917899
1988	57.92191805693563
1989	58.112389034028716
1990	56.47429755953741
1991	54.34996044108894
1992	53.83931718269104
1993	54.199414315492476
1994	55.15120786473339
1995	54.948551832403076
1996	54.94967638982766
1997	55.479423266276434
1998	56.657048988592386
1999	56.65003477570863
2000	57.220073589889985
2001	56.059741468927704
2002	54.5926884607579
2003	53.04823609506904
2004	52.793804489006156
2005	53.21791759484541
2006	53.013138619534914
2007	52.67113806129769
2008	51.23164317276965
2009	48.08367384720532
2010	46.292266303265414
2011	46.11289947630457
2012	46.53649002689463
2013	47.14483469051098
2014	48.09853256745035
2015	49.15019899577007
2016	49.63470603805923
2017	50.713376316083966
2018	51.104296634713286
2019	51.93645216179176
2020	45.749059808785255
2021	50.28086390069063
2022	51.45961310085464
2023	52.579807897178924