Year % 1997 14.55 2001 14.46 2002 14.46 2003 14.13 2004 14.13 2005 14.13 2006 14.13 2007 13.6 2008 13.6 2009 13.6 2010 13.6 2011 13.6 2013 14.57 2015 13.6 2016 13.6