Year 1=low to 6=high 2011 2.7 2012 2.7 2013 2.7 2014 2.7 2015 2.7 2016 2.6 2017 2.6 2018 2.6 2019 2.6 2020 2.7 2021 2.7 2022 2.7 2023 2.7