Year 1=low to 6=high 2005 3.1556306306306303 2006 3.153378378378379 2007 3.177252252252252 2008 3.1621621621621627 2009 3.1767543859649123 2010 3.1809210526315788 2011 3.204605263157895 2012 3.1739316239316233 2013 3.1709401709401708 2014 3.1864045614035086 2015 3.172149824561404 2016 3.136842105263159 2017 3.1017094017094027 2018 3.128508771929826 2019 3.1000000000000005 2020 3.109188034188035 2021 3.115598307692308 2022 3.127991487179487 2023 3.139743641025641