Year % 2005 4.37 2007 4.17 2008 4.2 2009 4.2 2011 4.7 2012 4.29 2013 4.32 2014 4.05 2015 4.03 2016 4.04 2017 4.15 2018 4.05 2019 4.07 2020 4.07 2021 4