Year Percent 2002 13.2 2003 13 2004 12.6 2005 12.6 2006 12 2007 15.2 2008 14.5 2009 14.7 2010 14.5 2011 14.4 2012 14.4 2013 14.1 2014 13.9 2015 14.1 2016 14.4 2017 14.3 2018 13.3 2019 13.9 2020 14.7 2021 14.8