Year % 1997 7.598006196955412 1998 7.659261077697313 2002 10.858799371904817 2003 11.246997160952171 2004 11.905492482356554 2005 14.309021113243768 2006 14.489152250788493 2007 15.60812800628252 2008 16.432676905681713 2009 16.84742647058824 2010 16.744016744016747 2011 18.191295282773 2012 18.96270895842263 2013 18.968642378104043 2014 19.18714555765596 2015 20.471195471195472 2016 20.620422940837653 2017 20.88842308932603 2018 20.668389032419377 2019 20.632644453816958 2020 21.87090575596123 2021 22.685104148433403 2022 23.16471877282688 2023 23.509872670234362