Year % (national estimate) 1976 42.42 1977 42.5 1978 42.5 1979 42.5 1980 42.49 1981 45.76 1982 45.7 1983 44.75 1984 44.73 1985 43.08 1986 42.42 1988 41.87 1989 17.9 1990 41.86 1991 41.76 1992 41.75 1993 40.3 1994 39.51 1995 39.06 1997 41.19 1998 40.26 2000 40.54 2002 43.42 2004 43.58 2005 37.652 2006 42.349 2007 41.273 2008 40.731 2009 41.077 2010 41.583 2011 40.248 2012 38.731 2013 41.404 2014 40.05 2015 40.294 2016 38.43 2018 40.039 2019 39.962 2021 43.737