Year % 1993 15.44 1997 16.93 1998 17.26 2001 15.16 2002 12.99 2003 11.97 2005 10.23 2006 9.93 2007 9.63 2008 9.2 2009 9.36 2014 8.35 2015 8.27 2016 8.85 2017 9.38 2018 9.98 2019 9.99 2020 10.16 2021 10.29