Year 1=low to 6=high 2005 3.32 2006 3.3137254901960786 2007 3.3627450980392157 2008 3.3823529411764706 2009 3.349056603773585 2010 3.3962264150943398 2011 3.4909090909090907 2012 3.526315789473684 2013 3.543103448275862 2014 3.5517241379310347 2015 3.5517241379310347 2016 3.543859649122807 2017 3.5 2018 3.5701754385964914 2019 3.5254237288135593 2020 3.5172413793103448 2021 3.508771929824561 2022 3.5254237288135593 2023 3.5254237288135593