Year % 1996 19.77 1997 19.77 1998 19.77 1999 19.77 2000 19.77 2001 19.77 2002 19.77 2003 20.37 2004 20.37 2005 20.37 2006 20.37 2007 20.37 2008 20.37 2009 20.91 2010 20.91 2011 20.91 2012 20.91 2013 20.91 2015 21.62 2016 21.62 2017 21.62 2019 21.77 2020 21.77 2021 21.77