Year % 2000 23.853502537528005 2001 23.805164209814297 2002 23.675505697959572 2003 23.600216098751584 2004 23.288752453486644 2005 22.995341940101248 2006 22.839963643653242 2007 22.579554131931374 2008 22.423761410340138 2009 22.237915599506927 2010 21.921443252732278 2011 21.551333209081328 2012 21.59609894348927 2013 21.212887748508606 2014 21.11978912586768 2015 21.265993268448018 2016 20.87574545625558 2017 20.520184499296214 2018 20.42809665842161 2019 20.300419388466572