Year	1=low to 6=high
2005	3.6
2006	3.6
2007	3.6
2008	3.6
2009	3.6
2010	3.6
2011	3.4
2012	3.4
2013	3.5
2014	3.6
2015	3.5
2016	3.5
2017	3.4
2018	3.4
2019	3.3
2020	3.3
2021	3.4
2022	3.4
2023	3.6