Year Percent 1998 27.04631 1999 24.90773 2000 24.45585 2001 24.1736 2002 24.3689 2003 24.37179 2004 31.64553 2005 30.77463 2006 29.93903 2007 29.04545 2008 29.196 2009 31.19894 2010 30.22184 2011 31.08369 2012 31.0858 2013 24.64255 2014 24.75704