Year	1=low to 6=high
2005	3.1
2006	3.1
2007	3.1
2008	3.2
2009	3.3
2010	3.4
2011	3.5
2012	3.4
2013	3.4
2014	3.4
2015	3.3
2016	3.3
2017	3.3
2018	3.4
2019	3.4
2020	3.4
2021	3.4
2022	3.6
2023	3.6