Year	1=low to 6=high
2005	3
2006	3.1
2007	3.3
2008	3.3
2009	3.3
2010	3.4
2011	3.4
2012	3.6
2013	3.6
2014	3.6
2015	3.6
2016	3.5
2017	3.5
2018	3.5
2019	3.5
2020	3.6
2021	3.6
2022	3.7
2023	3.7