Year % 2000 37.2 2001 36.8 2002 36.5 2003 36.2 2004 35.9 2005 35.5 2006 35 2007 34.8 2008 34.4 2009 33.9 2010 33.5 2011 33.2 2012 33.1 2013 33.1 2014 33.1 2015 33.1 2016 33.1 2017 33.1 2018 33.1 2019 33.2