Year Percent 1995 60.2218 1996 59.74319 1997 59.42334 1998 59.2511 1999 59.01372 2000 59.10313 2001 59.48968 2002 59.84321 2003 59.72143 2004 59.92408 2005 59.65283 2006 59.88627 2007 61.10083 2008 62.98228 2009 65.66653 2010 65.41799 2011 66.6681 2012 67.40411 2013 67.46414 2014 67.47105 2015 66.77762 2016 66.92814 2017 66.44386