Year % of adults 2004 1 2005 1.2 2006 1.5 2007 1.7 2008 2.2 2009 2.5 2010 2.9 2011 3.5 2012 4.3 2013 5.3 2014 5.8 2015 6.6 2016 7.1 2017 7.8 2018 8.4 2019 9.5