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