Year 1=low to 6=high 2005 3.2407407407407414 2006 3.261111111111111 2007 3.2870370370370368 2008 3.2888888888888888 2009 3.342592592592593 2010 3.314814814814815 2011 3.2870370370370368 2012 3.2192982456140355 2013 3.184210526315789 2014 3.2129622222222216 2015 3.1296292592592585 2016 3.0277777777777777 2017 2.912280701754385 2018 2.9351851851851856 2019 2.9122807017543857 2020 2.903508771929825 2021 2.912280736842105 2022 2.894736947368421 2023 2.912280684210527