Year Percent 2005 47.74 2006 47.89 2007 43.73 2008 35.25 2009 41.59 2010 46.26 2011 50.93 2012 51.05 2013 49.42 2014 47.53 2015 43.16 2016 34.94 2017 31.91 2018 29.72 2019 27.53 2020 26.65