Year % 1992 11.39 1993 8.92 1996 6.34 1997 5.59 1998 4.61 1999 3.86 2000 3 2001 4 2002 4.11 2003 4.5 2004 4.56 2005 4.01 2006 3.86 2007 3.52 2008 2.58 2009 2.41 2010 2.7 2011 2.33 2012 2.43 2013 2.43 2014 2.41 2015 2.43 2016 2.43 2017 2.44 2019 2.4 2020 2.33 2021 2.33