Year % 2000 35.3 2001 35.6 2002 36 2003 36.1 2004 36.2 2005 36.3 2006 36.3 2007 36.2 2008 36.3 2009 36.2 2010 36.1 2011 35.9 2012 35.7 2013 35.5 2014 35.8 2015 35.4 2016 34.5 2017 34.2 2018 33.8 2019 33.7