Year % 1991 19.08 1993 8.01 1994 11.11 1995 6.74 1996 8.58 1997 9.38 1998 6.43 1999 8.19 2000 7.76 2001 8.13 2002 8.12 2003 4.93 2004 6.38 2005 7.3 2006 4.97 2007 6.26 2008 5.75 2009 5.42 2010 4.71 2011 4.78 2012 5.34 2013 5.5 2014 5.5 2015 4.22 2016 3.94 2017 3.57