Year % 1993 24.41 1997 24.09 1998 23.95 2001 22.17 2002 19.22 2003 18.74 2005 18.72 2006 18.72 2007 18.57 2008 18.56 2009 18.56 2014 18.79 2015 18.77 2016 18.77 2017 18.88 2018 19.01 2019 19.02 2020 19.03 2021 19.03