Year % 2000 15.9 2001 15.2 2002 14.5 2003 14.8 2004 14.9 2005 14.7 2006 14.4 2007 13.6 2008 13 2009 12.1 2010 11.9 2011 11.4 2012 11.2 2013 11.1 2014 10.9 2015 11.2 2016 11.3 2017 11.2 2018 10.8 2019 10.8