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