Year % 1993 20.39 1997 23.15 1998 22.15 2001 20.81 2002 19.75 2003 18.58 2005 15.92 2006 15.82 2007 16.89 2008 17.22 2009 14.53 2014 16.16 2015 15.72 2016 14.61 2017 14.52 2018 14.68 2019 14.72 2020 14.72 2021 14.95