Year	1=low to 6=high
2005	3.4
2006	3.5
2007	3.5
2008	3.4
2009	3.4
2010	3.4
2011	3.4
2012	3.2
2013	3
2014	3
2015	3
2016	3.1
2017	3.1
2018	3.1
2019	3.1
2020	3.2
2021	3.3
2022	3.3
2023	3.3