Year	1=low to 6=high
2005	2.5
2006	2.5
2007	2.4
2008	2.5
2009	2.6
2010	2.4
2011	2.7
2012	2.8
2013	3
2014	3.1
2015	3.1
2016	3.2
2017	3.2
2018	3.3
2019	3.5
2020	3.5
2021	3.5
2022	3.6
2023	3.7