Year 1=low to 6=high 2005 3.5 2006 3.5 2007 3.5 2008 3.5 2009 3 2010 3 2011 3 2012 3 2013 3 2014 3 2015 3 2016 2.5 2017 2.5 2018 2.5 2019 2 2020 2 2021 2 2022 2 2023 1.5