Year % (national estimate) 1999 37.16 2000 37.05 2001 36.38 2002 34.78 2003 38.22 2004 32.21 2005 33.81 2006 30.7 2007 31.2 2008 36.16 2009 38.521 2010 39.439 2011 41.227 2012 41.704 2013 40.749 2014 41.446 2015 42.373 2016 39.885 2017 44.438 2018 40.443 2019 38.078 2020 38.869