Year % of adults 2004 4.694444444444443 2005 4.161363636363635 2006 5.404444444444444 2007 6.266666666666667 2008 8.591111111111111 2009 11.286956521739127 2010 12.923913043478262 2011 14.152173913043475 2012 15.600000000000001 2013 17.892156862745097 2014 18.547058823529415 2015 21.531372549019608 2016 21.47254901960784 2017 22.380392156862747 2018 23.25882352941177 2019 22.484313725490196