Year % 2001 15.46 2002 15.36 2003 15.33 2004 15.41 2005 15.37 2006 13.39 2007 13.25 2008 13.25 2009 13.25 2010 13.25 2011 13.24 2012 13.24 2013 13.25 2014 13.32 2015 14.29 2016 13.04 2017 18.44 2018 18.16 2019 15.31 2020 15.31 2021 14.49