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 3.5 2018 3.5 2019 3.5 2020 3.5 2021 3.5 2022 3 2023 2.5