Year	1=low to 6=high
2005	2.4
2006	2.4
2007	2.2
2008	2.2
2009	2.2
2010	2.2
2011	2.2
2012	2.2
2013	2.4
2014	2.6
2015	2.7
2016	2.7
2017	2.7
2018	2.6
2019	2.5
2020	2.6
2021	2.5
2022	2.5
2023	2.4