Year % 1996 15.22 1997 15.56 1999 15.46 2000 14.35 2001 14.27 2002 14.23 2003 14.55 2004 14.56 2005 14.61 2006 14.15 2007 13.85 2008 13.85 2009 13.84 2010 13.53 2011 13.66 2012 13.14 2013 12.88 2014 12.87 2015 11.84 2016 12.08 2017 13.31 2018 13.13 2019 11.83 2020 11.83 2021 11.33