Year	% (national estimate)
1961	33.5921052631579
1970	39.22197434467373
1977	52.967194987099155
1979	55.53308823529412
1980	56.74126132790826
1981	54.641350210970465
1983	55.04360354894972
1984	55.980942921878395
1985	56.544259041002434
1986	57.94030459400537
1987	58.44164148801817
1988	59.1192928391858
1989	58.859576404804855
1990	59.88008256610202
1991	61.90406384884762
1992	63.61257828724675
1993	65.28969249043158
1994	65.66878668476039
1995	66.25635492782763
1996	66.58456890465166
1997	67.59421054366818
1998	68.69434733856605
1999	70.5085908407918
2000	70.96706012421552
2001	69.19364701604773
2002	70.53414626064483
2003	71.25035252741418
2004	73.37976782752902
2005	74.43997328163438
2006	75.2945429449365
2007	76.17846909537455
2008	77.09500879254523
2009	77.76397515527951
2010	78.47849329714614
2011	78.7607803734405
2012	78.84164713759625
2013	80.0606710689505
2014	81.17581508433655
2015	81.52733200876254
2016	81.3641008174387
2017	82.33733310799391
2018	83.88982060273416
2019	84.28129281039118
2020	84.36751727440651
2021	84.65313028764805
2022	85.31318219983208
2023	85.25795219431782