Year % of adults 2004 0.2 2005 0.2 2006 0.1 2007 0.2 2008 0.3 2009 0.2 2010 0.2 2011 0.3 2012 0.3 2013 0.3 2014 3.9 2015 4.4 2016 4 2017 4.6 2018 4 2019 6.5