Year 1=low to 6=high 2005 3.5 2006 3.5 2007 3.5 2008 3.5 2009 3.5 2010 3 2011 3 2012 3 2013 3 2014 3 2015 3 2016 3 2017 3 2018 3 2019 3 2020 3 2021 3 2022 3 2023 3.5