Year % 1996 19.92 1999 17.13 2000 17.28 2001 10.88 2002 10.92 2003 10.9 2006 10.59 2007 11.08 2008 9.6 2009 10.93 2010 9.56 2011 8.92 2012 8.92 2013 9.87 2015 8.85 2016 8.78 2017 8.63 2018 8.75 2019 7.75 2020 8.38 2021 8.18