Year Percent 2005 4.88 2006 3.65 2007 3.41 2008 3 2009 4.25 2010 5.67 2011 3.88 2012 3.4 2013 3.1 2014 2.84 2015 3.53 2016 4.6 2017 3.89 2018 4.32 2019 3.04 2020 3.22