Year % 1989 44.42 1990 34.91 1991 28.74 1992 23.88 1993 16.64 1994 15.29 1995 13.84 1996 15.43 1997 15 1998 17.73 1999 16.47 2000 17.21 2001 15.35 2002 15.15 2003 14.79 2004 13.61 2005 12.74 2006 12.56 2007 12.6 2008 13.63 2009 13.87 2010 13.9 2011 14.01 2012 14.31 2013 15.34 2014 14.31 2015 14.21 2016 14.13 2017 13.96 2018 14.01 2019 13.99 2020 14.11 2021 13.73