Year Percent 2004 57.42459 2006 64.03664 2007 69.46887 2008 71.66752 2009 57.23704 2010 67.22956 2011 68.09471 2012 74.01124 2013 77.23456 2014 80.19374 2015 85.01027 2016 88.73115 2017 94.29651