Year % 1993 18.53 2000 21.02 2001 17.31 2002 17.31 2003 17.31 2007 16.74 2008 16.63 2009 16.71 2010 17.04 2013 16.2 2016 15.23 2017 15.94 2018 16.15 2019 16.1 2020 15.94 2021 15.94