Year	% (national estimate)
1968	57.129
1969	56.032
1970	56.492
1971	57.76
1972	56.115
1973	54.127
1974	51.674
1975	48.495
1976	46.611
1977	44
1978	42.91
1979	42.157
1980	41.169
1981	41.514
1982	41.333
1983	41.924
1984	41.074
1985	40.457
1986	40.447
1987	39.913
1988	40
1989	40.313
1990	41.443
1991	42.958
1992	44.557
1993	45.297
1994	45.351
1995	45.073
1996	45.601
1997	45.967
1998	44.824
1999	42.79
2000	42.288
2001	41.118
2002	40.459
2003	39.756
2004	38.813
2005	39.669
2006	40.245
2007	40.932
2008	40.625
2009	37.957
2010	37.638
2011	37.732
2012	37.355
2013	38.321
2014	39.398
2015	40.251
2016	42.118
2017	41.891
2018	44.746
2019	46.042
2020	45.437
2021	45.603
2022	45.183
2023	46.523