Year % 1996 4.37 1997 4.37 1998 4.37 1999 4.37 2000 4.37 2001 4.37 2002 4.4 2003 4.4 2004 4.41 2005 4.41 2006 4.41 2007 4.42 2008 4.42 2009 4.42 2010 4.42 2011 4.43 2012 4.24 2013 4.23 2014 4.23 2015 4.23 2016 4.23 2017 4.24 2019 4.24 2020 4.24 2021 4.24