Year	% (national estimate)
1960	48.06
1966	48.94
1970	47.89
1975	50.88
1980	46.392
1981	43.95
1982	43.023
1983	38.307
1984	34.805
1985	32.952
1986	31.724
1987	30.734
1988	28.28
1989	28.332
1990	28.353
1991	31.291
1992	31.683
1993	30.778
1994	31.774
1995	31.199
1996	30.587
1997	29.197
1998	27.75
1999	27.889
2000	26.276
2001	26.425
2002	27.203
2003	26.911
2004	27.449
2005	25.111
2006	22.982
2007	21.645
2008	19
2009	18.546
2010	18.237
2011	19.492
2012	20.078
2013	20.649
2014	22.95
2015	24.231
2016	24.365
2017	24.315
2018	22.681
2019	24.206
2020	22.886
2021	23.323
2022	24.753
2023	22.794