Year % 1997 8.006672226855715 1998 7.990970654627543 1999 7.848309975267931 2002 11.018678386438548 2003 11.453870322764924 2004 12.022703818369457 2005 14.85407980941037 2006 14.997064004697595 2007 16.235180256472297 2008 17.14252553389044 2009 17.576579631513514 2010 17.4670538306902 2011 19.113924050632917 2012 19.979220779220782 2013 19.13496376811594 2014 19.3991690635986 2015 21.05101098224366 2016 21.20598947794415 2017 21.417291748914334 2018 21.152856407617094 2019 21.157663775989977 2020 22.20159440864913 2021 23.243598161523316 2022 23.75620454807804 2023 24.16491473954684