Year 1=low to 6=high 2005 3.5 2006 3.5 2007 3.5 2008 3.5 2009 3.5 2010 3.5 2011 4 2012 4 2013 4 2014 4 2015 4 2016 4 2017 4 2018 4 2019 4.5 2020 4.5 2021 4.5 2022 4.5 2023 4.5