Year	% (national estimate)
1975	45.98
1993	50.8
1995	52.8
1997	48.1
1999	47.9
2000	51.3
2001	47.5
2002	47.05
2003	43.14
2006	42.07
2007	40.52
2008	39.45
2009	39.44
2010	39.02