Year 1=low to 6=high 2005 3.21 2006 3.156862745098039 2007 3.215686274509804 2008 3.196078431372549 2009 3.169811320754717 2010 3.1320754716981134 2011 3.1272727272727274 2012 3.1140350877192984 2013 3.1120689655172415 2014 3.103448275862069 2015 3.060344827586207 2016 3.0350877192982457 2017 2.9655172413793105 2018 2.956140350877193 2019 2.889830508474576 2020 2.8793103448275863 2021 2.93859649122807 2022 2.940677966101695 2023 2.940677966101695