Year % 1992 15.17 1993 10 1996 6.85 1997 6.17 1998 5.06 1999 4.12 2000 3.43 2001 3.86 2002 4.54 2003 5.1 2004 5.64 2005 4.24 2006 4.06 2007 4 2008 2.99 2009 2.71 2010 2.76 2011 3 2012 3.1 2013 2.49 2014 2.29 2015 2.29 2016 2.24 2017 2.24 2019 2.12 2020 2.03 2021 2.02