Year % 1995 28.1 1996 28.2 1997 28.2 1998 28.2 1999 28.2 2000 11.45 2001 9.47 2002 10.28 2003 9.3 2004 9.18 2005 9.2 2006 8.91 2007 8.37 2008 8.39 2009 8.42 2010 8.39 2011 8.43 2012 7.02 2013 8.18 2014 7.02 2015 8 2016 8 2017 6.86