Year % 2001 13.79 2002 13.71 2003 13.82 2004 13.82 2005 13.85 2006 13.37 2007 13.32 2008 13.32 2009 13.31 2010 13.29 2011 13.17 2012 12.98 2013 12.98 2014 13.03 2015 12.57 2016 12.62 2017 12.71 2018 12.59 2019 12.42 2020 12.41 2021 12.52