Year % of adults 2005 2.4 2006 2.4 2007 1.9 2008 2.7 2009 3 2010 2.5 2011 2.9 2012 3.9 2013 4.7 2014 5.1 2015 7.5 2016 9 2017 6.3 2018 8.7 2019 10.8