Year	1=low to 6=high
2005	3.4
2006	3.4
2007	3.5
2008	3.5
2009	3.4
2010	3.2
2011	3.3
2012	3.3
2013	3.4
2014	3.5
2015	3.4
2016	3.5
2017	3.6
2018	3.5
2019	3.5
2020	3.5
2021	3.6
2022	3.6
2023	3.7