Year	1=low to 6=high
2005	4.2
2006	4.2
2007	4.2
2008	4.1
2009	4.1
2010	4.2
2011	3.9
2012	3.9
2013	3.9
2014	3.9
2015	3.9
2016	3.9
2017	3.6
2018	3.4
2019	3.2
2020	3.2
2021	3.2
2022	3.2
2023	3.2