Year	1=low to 6=high
2005	3.4
2006	3.4
2007	3.4
2008	3.4
2009	3.4
2010	3.4
2011	3.3
2012	3.3
2013	3.1
2014	3.1
2015	3.1
2016	3.2
2017	3.2
2018	3.2
2019	3
2020	3
2021	3
2022	2.9
2023	3