Year Percent 2000 14.9683 2001 15.14129 2002 15.31429 2003 15.48728 2004 15.83182 2005 16.18015 2006 16.53226 2007 16.88817 2008 17.24787 2009 17.61136 2010 17.97863 2011 18.3497 2012 18.72456 2013 19.1032 2014 19.48564 2015 19.87187 2016 20.26189 2017 20.65569 2018 21.05329 2019 21.45468 2020 21.85985 2021 22.26882 2022 22.26882