Year	1=low to 6=high
2005	3.9
2006	4
2007	4
2008	4
2009	3.9
2010	3.9
2011	3.9
2012	3.9
2013	3.9
2014	3.8
2015	3.8
2016	3.7
2017	3.7
2018	3.8
2019	3.8
2020	3.8
2021	3.8
2022	3.8
2023	3.9