Year % 1995 15.92 1997 15.92 2001 20.49 2002 20.85 2003 23.45 2004 24.84 2005 21.84 2006 22.11 2007 18.23 2008 17.14 2009 18.16 2010 17.66 2011 18.42 2013 19.11 2015 20.98 2016 17.53