Year Percent 2000 20.59397 2001 20.54728 2002 20.50059 2003 20.45361 2004 20.40632 2005 19.97215 2006 19.54504 2007 19.12489 2008 18.71103 2009 18.30309 2010 17.90095 2011 17.50401 2012 17.11216 2013 16.72504 2014 16.34208 2015 15.96319 2016 15.58824 2017 15.21649 2018 14.84784 2019 14.48198 2020 14.11863 2021 13.75751 2022 13.84629