Year % 2001 15.052855391421394 2002 16.66600868962172 2003 17.386714241746887 2004 17.18312231119004 2005 15.023007485486477 2006 15.923455499389977 2007 17.091135826219706 2008 16.149944059967893 2009 20.341627619062894 2010 22.891797876415147 2011 20.221029548677873 2012 19.571980002179487 2013 20.410211433681283 2014 21.195473638625927 2015 22.503945249978948 2016 22.163441529766462 2017 20.267657162845158 2018 21.734522183702563 2019 21.277825096468295 2020 22.104320881741263 2021 22.226700342439162 2022 21.389311852347554 2023 20.738920186816785