Year	1=low to 6=high
2005	3.8
2006	3.8
2007	3.8
2008	3.8
2009	3.9
2010	3.9
2011	3.9
2012	3.9
2013	3.9
2014	3.9
2015	3.8
2016	3.9
2017	3.9
2018	4.1
2019	4
2020	4
2021	4
2022	4
2023	4