Year	1=low to 6=high
2005	3.6
2006	3.5
2007	3.5
2008	3.5
2009	3.7
2010	3.7
2011	3.7
2012	3.7
2013	3.7
2014	3.5
2015	3.5
2016	3.5
2017	3.4
2018	3.4
2019	3.2
2020	3.4
2021	3.4
2022	3.2
2023	3.2