Year Percent 1995 19.34561 1996 18.6726 1997 22.25833 1998 23.63521 1999 22.67019 2000 20.77011 2001 20.69071 2002 19.98483 2003 20.24453 2004 20.41818 2005 21.54094 2006 22.24857 2007 21.71421 2008 20.82915 2009 18.83515 2010 19.81146 2011 20.04159 2012 21.10078 2013 21.97728 2014 22.41082 2015 22.76692 2016 23.88407