Year	1=low to 6=high
2005	3.5
2006	3.5
2007	3.6
2008	3.6
2009	3.6
2010	3.7
2011	3.6
2012	3.6
2013	3.5
2014	3.2
2015	3.1
2016	3.1
2017	3.1
2018	3.1
2019	3.2
2020	3.2
2021	3.2
2022	3.2
2023	3.2