Year Percent 2004 0.26962 2006 0.25372 2007 0.2478 2008 0.2423 2009 0.31544 2010 0.30844 2011 0.30053 2012 0.29314 2013 0.28482 2014 0.27684 2015 0.26955 2016 0.26326 2017 0.38455 2018 0.41173 2019 0.36891 2020 0.36303