Year Number 2007 0.674840748310089 2008 0.495077729225159 2009 0.447026580572128 2010 0.436017781496048 2011 0.433710306882858 2012 0.445544064044952 2013 0.477508425712585 2014 0.737446308135986 2015 0.425994992256165 2016 0.48630765080452 2017 0.456809163093567 2018 0.472319453954697 2019 0.469669729471207 2020 0.49580055475235 2021 0.458972722291946 2022 0.397816181182861