Year % 1996 19.24 1999 14.74 2000 14.99 2001 14.5 2002 14.6 2003 14.09 2006 13.27 2007 14.09 2008 12.42 2009 14.23 2010 13.25 2011 13.99 2012 13.49 2013 14.17 2015 13.36 2016 14.64 2017 14.48 2018 13.54 2019 17.44 2020 18.15 2021 18.24