Year % 1997 16.31 2000 10.59 2001 10.6 2002 7.28 2003 6.94 2004 6.31 2005 6.05 2006 5.55 2007 5.36 2008 5.13 2009 4.94 2010 4.94 2011 4.95 2012 3.46 2013 3.46 2014 3.46 2015 3.44 2016 3.44 2017 3.37 2018 3.32 2019 3.32 2020 3.32 2021 3.32