Year	% (national estimate)
1960	73.04
1970	70.43
1980	70.23
1983	39.9
1986	50.19
1988	55.13
1990	75.77
2002	48.9
2004	53.1
2005	52.5
2006	54.2
2007	45.4
2009	49.5
2011	47.5