Year % of adults 2004 1.1 2005 1.2 2006 1.2 2007 1.3 2008 1.3 2009 1.4 2010 1.4 2011 1.7 2012 1.8 2013 1.7 2014 2 2015 2.2 2016 2.3 2017 2.2 2018 2.2 2019 2.2