Year Percent 2006 13.66 2007 15.98 2008 13.96 2009 14.68 2010 14.65 2011 16.16 2012 15.38 2013 16.46 2014 13.27 2015 14.61 2016 15.86 2017 11.17 2018 10.46 2019 8.74 2020 9.85