Year	% (national estimate)
1960	23.33
1970	51.14
1980	45.57
1983	36.72
1986	42.95
1988	39.51
1990	55.47
2002	38.5
2004	41.4
2005	50.4
2006	49
2007	44.4
2009	39.3
2011	44.7