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