Year % 2000 23.896425876149337 2001 23.603724081708528 2002 23.384426945126034 2003 23.203352412341253 2004 22.98556797643596 2005 22.802241432073757 2006 22.66823328733992 2007 22.53765648036904 2008 22.38412322768333 2009 22.256669841303314 2010 22.154090132414154 2011 22.144021842582138 2012 22.18270626917189 2013 22.245918561350546 2014 22.31937938358775 2015 22.392106949138 2016 22.529065139583913 2017 22.636278349299666 2018 22.739436866506335 2019 22.828261923849247