Year % 1993 21.89 1997 23.54 1998 23.72 2001 21.63 2002 19.79 2003 19.37 2005 19.36 2006 19.35 2007 19.6 2008 19.6 2009 19.6 2014 20.52 2015 20.54 2016 20.54 2017 20.62 2018 20.72 2019 20.74 2020 20.74 2021 20.74