Year % 1996 22.74 1999 23.76 2001 19.73 2002 19.82 2003 19.14 2006 16.05 2007 15.46 2008 15.75 2009 18.65 2010 18.94 2011 16.14 2012 16.24 2013 16.9 2014 16.9 2015 16.79 2016 17.01 2017 16.95 2018 16.65 2019 16.31 2020 24.15 2021 24.36