Year % 2001 15.14805630068315 2002 17.222981755266893 2003 16.892675388368602 2004 18.149058109559057 2005 18.869507756685724 2006 17.617572656611785 2007 19.429464292191764 2008 17.530187012738956 2009 19.03556207142988 2010 19.155018959104503 2011 17.023971488975512 2012 18.40068321391709 2013 21.042458807427444 2014 19.467645152323634 2015 18.60684681165294 2016 18.420278799793575 2017 19.253811751906458 2018 18.703254394611957 2019 18.855371391926063 2020 18.664986665697565 2021 19.68823850966662 2022 17.304066881908923 2023 15.472605848930435