Year % 1996 27.28 1999 24.72 2000 24.9 2001 19.38 2002 20.09 2003 19.8 2006 17.82 2007 22.04 2008 16.15 2009 19.82 2010 15.6 2011 15.87 2012 15.64 2013 16.04 2015 16.63 2016 17.03 2017 17.38 2018 17.62 2019 19.91 2020 16.92 2021 17.33