Year	1=low to 6=high
2005	3.6
2006	3.5
2007	3.5
2008	3.4
2009	3.4
2010	3.4
2011	3.3
2012	3
2013	3
2014	3
2015	3
2016	3
2017	3
2018	3
2019	3.1
2020	2.7
2021	2.6
2022	2.4
2023	2.3