Year % 1991 19.87 1993 11.01 1996 6.91 1997 6.93 1998 6.6 1999 6.21 2000 5.95 2001 4.91 2002 3.99 2003 4.05 2004 4 2005 3.3 2006 4.09 2007 4.26 2008 3.88 2009 3.96 2010 3.61 2011 2.47 2012 2.58 2013 2.63 2014 2.69 2015 2.72 2016 2.71 2017 2.9 2018 2.86 2019 2.72 2020 2.73 2021 2.86