Year % 2000 15.8 2001 15.5 2002 15 2003 14.8 2004 14 2005 14.2 2006 13.5 2007 13.1 2008 12.9 2009 12.7 2010 12.4 2011 12.2 2012 12.1 2013 11.8 2014 11.5 2015 11.5 2016 11.5 2017 11.3 2018 11.4 2019 11