Year % 2001 19.229377304290786 2002 18.621171614663456 2003 17.221107517259476 2004 19.637833339937394 2005 19.3265172829582 2006 17.617572656611785 2007 20.70491248484215 2008 17.997260801068634 2009 20.3589468116486 2010 20.23541452515861 2011 22.16826412919537 2012 22.042638129365642 2013 23.608376904575756 2014 21.73593643542047 2015 21.846723297255622 2016 18.718436476922413 2017 21.889413543389903 2018 19.17343169338096 2019 18.879463522894525 2020 19.45898186152704 2021 19.787851126982847 2022 17.304066881908923 2023 15.101247221980397