Year % 1997 11.54 1998 7.96 1999 7.88 2000 7.7 2001 7.52 2002 7.49 2003 7.32 2004 7.34 2005 6.95 2006 7.17 2007 6.97 2008 6.87 2009 7.34 2010 7.08 2011 6.93 2012 6.82 2013 6.42 2015 7.06 2020 5.48 2021 5.3