Year % 1996 38.48 1997 20.07 1998 20.55 1999 23.5 2000 22.93 2001 19.17 2002 18.44 2003 18.25 2007 17.1 2010 16.77 2011 16.53 2012 16.28 2015 18.52 2016 16.08 2021 18.6