Year % 1997 8.709946769648262 1998 10.942578548212358 1999 11.0249742407144 2000 11.432834429057676 2001 11.988685813751085 2002 13.267123897746504 2003 13.045634920634926 2004 13.832190559232695 2005 14.50384557381994 2006 15.000187596143023 2007 15.911054351500582 2008 16.49220489977728 2009 17.236347718235873 2010 17.407809110629064 2011 18.17626338868521 2012 19.276385457112596 2013 19.987519271712802 2014 20.41210795040117 2015 21.111513396089794 2016 21.449052381285412 2017 21.856717463653876 2018 22.190516451772005 2019 22.532900478235067 2020 23.49691948162312 2021 24.019312009656005 2022 24.471760555696985 2023 24.848884492801407