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