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