Year	% (national estimate)
1961	22.6048071548351
1971	28.18725099601594
1975	38.5008896797153
1977	37.016438017550364
1979	36.941729555857975
1981	36.884021901443504
1982	36.26168224299066
1983	36.74676059881746
1984	38.45962732919255
1985	37.842170160295936
1986	38.07175440759462
1987	38.66074731779504
1988	39.11879259980526
1989	42.62636152245747
1990	46.202453227605005
1991	47.708563705614935
1992	46.93221177634834
1993	45.49113319079361
1994	46.060755742158555
1995	50.182793078235434
1996	52.54854368932038
1997	55.82547739908146
1998	57.21153846153846
2001	63.47479143997099
2002	65.43519846963176
2005	62.21039488453631
2006	62.43213490455102
2007	62.52394394596229
2008	62.724997471938515
2009	63.68579597671806
2010	63.13211205796805
2011	63.58443092248839
2012	64.1032298265656
2016	63.80121335221958
2017	67.57076808727749
2020	64.97524752475248