Year Percent 1998 34.7165 1999 33.45153 2000 33.96201 2001 32.02379 2002 31.35122 2003 31.07815 2004 23.87014 2005 23.28688 2006 23.32975 2007 23.64241 2008 24.17084 2009 27.59751 2010 24.65824 2011 28.09955 2012 20.75625 2013 24.71208 2014 22.81701