Year	1=low to 6=high
2005	3.6
2006	3.6
2007	3.5
2008	3.5
2009	3.4
2010	3.6
2011	3.5
2012	3.4
2013	3.3
2014	3.2
2015	3.3
2016	3.3
2017	3.3
2018	3.3
2019	3.4
2020	3.4
2021	3.4
2022	3.4
2023	3.5