Year % 1997 16.885917619150316 1998 17.949298325033958 1999 18.23885525591634 2000 19.41747572815534 2001 18.957345971563978 2002 20.12927054478301 2003 20.724543080939945 2004 21.670478057279755 2005 22.03407880724174 2006 22.775649212430817 2007 23.65762892078682 2008 24.31772326643306 2009 24.737456242707125 2010 24.854204220125126 2011 25.319420783645658 2012 25.939329430548163 2013 27.47800275628114 2014 28.12838863587074 2015 28.56524561783164 2016 28.562155144433632 2017 29.571566627295173 2018 30.42777300085984 2019 31.972496776966057 2020 32.935355491018605 2021 33.51931330472103 2022 33.571664283357165 2023 33.52266399376322