Year % 2000 29.1 2001 28.9 2002 28.8 2003 28.3 2004 28.3 2005 27.8 2006 26.8 2007 27 2008 25.9 2009 25.2 2010 24.4 2011 24.1 2012 24.1 2013 23.6 2014 23.4 2015 23.5 2016 23.2 2017 23.1 2018 23.2 2019 23.2