Year % 1995 19.3 1998 19.29 2000 19.04 2001 19.17 2002 19.17 2003 19.36 2004 19.36 2005 19.08 2007 19.18 2008 19.13 2009 19.13 2010 19.15 2011 19.15 2012 18.78 2013 18.78 2015 18.78 2016 18.78 2019 18.8