Year	1=low to 6=high
2005	3.5
2006	3.4
2007	3.4
2008	3.4
2009	3.4
2010	3.2
2011	3.2
2012	3.2
2013	3.3
2014	3.3
2015	3.3
2016	3.2
2017	3.2
2018	3.1
2019	3
2020	2.9
2021	2.8
2022	2.6
2023	2.4