Year % 1997 2.95 2001 2.81 2002 2.37 2003 2.37 2005 2.37 2006 2.37 2007 2.37 2008 1.71 2009 1.71 2010 1.71 2011 1.71 2012 1.71 2014 1.71 2016 1.71 2018 1.53 2020 1.53 2021 1.53