Year	% (national estimate)
1960	75.84
1970	75.77
1980	72.68
2000	53.43
2001	51.5
2002	50.29
2003	52.02
2004	50.88
2005	50.41
2006	49.18
2007	49.13
2008	48.56
2009	48.29
2010	45.86
2011	49.31
2012	47.92
2013	46.94
2014	47.11
2015	46.73