Year % of adults 2004 1.8 2005 2.9 2006 2.9 2007 2.3 2008 2.7 2009 2.5 2010 2.4 2011 1.8 2012 1.8 2013 2.4 2014 1.8 2015 3.3 2016 1.9 2017 1.9 2018 1.6 2019 1.5