Year	% (national estimate)
1976	34.63
1977	33.95
1978	33.5
1979	33.08
1981	31.5
1982	29.11
1983	32.51
1984	34.04
1985	33.91
1986	36.21
1987	38.15
1988	40.48
1990	41.35
1991	41.07
1992	38.84
1993	39.07
1995	40.32
1996	41.3
1997	41.76
1998	41.29
1999	40.95
2000	41.06
2002	39.86
2003	40.3
2004	40.64
2005	42.29
2006	42
2007	41.07
2008	39.65
2009	36.7
2010	35.1
2011	34.1
2012	35.6
2015	35.21