Year % 2005 4.68 2007 4.19 2008 4.2 2009 4.2 2011 4.44 2012 3.67 2013 3.8 2014 3.43 2015 3.19 2016 3.32 2017 3.53 2018 2.99 2019 3.23 2020 3.25 2021 2.92