Year % 1988 13.76 1990 11.41 1991 12.3 1993 14.23 1996 8.84 1997 7.01 1999 6.13 2000 6.16 2001 5.97 2002 5.7 2003 5.96 2004 6.48 2005 6.79 2006 6.61 2007 5.99 2008 5.06 2009 5.49 2010 5.7 2011 5.63 2012 5.5 2013 5.36 2014 5.28 2015 5.37 2016 5.25 2017 5.28 2018 5.32 2019 5.29 2020 5.03 2021 5.06