Year % of adults 2004 2.176470588235294 2005 2.3235294117647065 2006 3.2411764705882358 2007 3.7941176470588234 2008 5.235294117647059 2009 5.276470588235294 2010 6.329411764705882 2011 7.935294117647059 2012 8.738888888888889 2013 11.475000000000001 2014 10.975 2015 14.395 2016 15.290000000000001 2017 16.35 2018 17.32 2019 16.865000000000002