Year % 1997 17.78 1998 10.48 1999 11.89 2000 11.85 2001 11.33 2002 13.44 2003 11.72 2004 11.67 2005 11.17 2006 11.92 2007 11.46 2008 11.29 2009 11.58 2010 11.14 2011 10.56 2012 10.89 2013 10.83 2015 11.22 2020 11.73 2021 11.39