Year Percent 2005 53.53896 2006 54.69429 2007 57.04289 2008 57.04912 2009 57.88959 2010 62.27782 2011 61.23331 2012 66.34238 2013 66.70041 2014 66.73026 2015 65.11352 2016 64.56923