Year Percent 2000 51.09814 2001 51.79044 2002 52.542 2003 53.35042 2004 54.21503 2005 55.13172 2006 56.10058 2007 57.11857 2008 58.1838 2009 59.29179 2010 60.44136 2011 61.62961 2012 62.85389 2013 63.67151 2014 63.92647 2015 64.1786 2016 64.42552 2017 64.66582