Year	% (national estimate)
1961	39.93
1971	40.84
1977	40.17
1978	39.15
1979	39.9
1980	41.2
1981	49.5
1982	41.46
1983	43.169
1984	42.839
1985	42.187
1986	43.827
1987	43.145
1988	44.549
1989	44.965
1990	43.033
1991	41.607
1992	37.692
1993	36.19
1994	34.074
1995	33.628
1996	34.028
1997	33.884
1998	33.101
1999	33.795
2000	33.965
2001	32.461
2002	30.896
2003	30.132
2004	31.945
2005	28.734
2006	26.863
2007	25.433
2008	25.526
2009	23.671
2010	23.121
2011	22.791
2012	23.995
2013	23.402
2014	23.084
2015	21.68
2016	22.753
2017	22.118
2018	21.91
2019	22.026
2020	18.784
2021	20.134
2022	21.529
2023	21.64