Year 1=low to 6=high 2005 3.1672727272727266 2006 3.1410714285714283 2007 3.1584905660377354 2008 3.1641509433962263 2009 3.1907407407407398 2010 3.1944444444444433 2011 3.1927272727272724 2012 3.199999999999999 2013 3.185964912280701 2014 3.171153846153847 2015 3.1788461538461528 2016 3.1714285714285717 2017 3.16734693877551 2018 3.159183673469387 2019 3.1540000000000004 2020 3.1291666666666664 2021 3.129166666666667 2022 3.1163265306122456 2023 3.1244897959183677