Year % 1996 22.39 1997 27.24 1998 27.24 1999 21.58 2000 21.26 2001 25.29 2002 24.36 2003 24.21 2006 19.23 2007 19.24 2010 18.44 2011 14.64 2012 14.45 2013 18.53 2015 24.83 2016 18.67 2017 18.26 2020 19.32