Year	1=low to 6=high
2006	2.3
2007	2.2
2008	2.2
2009	2.4
2010	2.4
2011	2.5
2012	2.5
2013	2.5
2014	2.5
2015	2.5
2016	2.6
2017	2.6
2018	2.6
2019	2.6
2020	2.6
2022	1.7
2023	1.6