Year % 1997 14.511278195488726 1998 15.159627206028164 1999 16.055572965632507 2000 16.562282533054976 2001 16.53758972421609 2002 18.335267433273547 2003 17.76365705614567 2004 18.812457553119238 2005 19.161619984859957 2006 19.532967032967033 2007 21.00993528393037 2008 21.348832918165886 2009 21.894621894621896 2010 21.99346998004716 2011 22.704174228675132 2012 23.75078779148285 2013 24.79762547220723 2014 25.348495964783567 2015 25.74311926605505 2016 26.005879110784498 2017 27.384785208352497 2018 27.95383769921231 2019 29.455944312145082 2020 30.29414459818565 2021 31.13371826597012 2022 30.923279428356526 2023 31.117994931005352