Year 1=low to 6=high 2005 4.5 2006 5 2007 5 2008 5 2009 5 2010 5 2011 4.5 2012 4.5 2013 4.5 2014 4.5 2015 4.5 2016 5 2017 5 2018 4.5 2019 4.5 2020 4.5 2021 4.5 2022 4.5 2023 4.5