Year	1=low to 6=high
2005	2.3
2006	2.2
2007	2.2
2008	2.2
2009	2.4
2010	2.4
2011	2.4
2012	2.5
2013	2.4
2014	2.4
2015	2.6
2016	2.7
2017	2.6
2018	2.6
2019	2.5
2020	2.4
2021	2.2
2022	2.1
2023	2.1