Year % 2000 20.641502182595374 2001 20.056943188731843 2002 19.667431976937078 2003 19.312449235689545 2004 18.694110783701195 2005 18.339837061251853 2006 17.850090909484873 2007 17.56030649499283 2008 17.249354762672947 2009 17.009199477771507 2010 16.671816447277248 2011 16.30536357615976 2012 16.035585085994136 2013 15.769803883895888 2014 15.501628509281582 2015 15.5023336565932 2016 15.408809567144093 2017 15.110235271609598 2018 14.870055011141648 2019 14.653065282725892