Year % 1996 15.37 1997 15.37 1999 14.97 2000 14.97 2001 14.97 2002 14.97 2003 14.61 2004 14.61 2005 14.61 2006 14.61 2007 14.04 2008 14.04 2009 14.04 2010 14.04 2011 14.04 2012 14.04 2013 14.04 2014 14.04 2015 14.99 2016 14.99 2017 15.2 2018 15.2 2019 15.2 2020 15.2 2021 15.2