Year Number 2004 0.410197407007217 2005 0.265190988779068 2006 0.31173050403595 2007 0.326607048511505 2008 0.326600551605225 2009 0.326186150312424 2010 0.315153837203979 2011 0.323667377233505 2012 0.325496852397919 2013 0.318169206380844 2014 0.353842169046402 2015 0.338430404663086 2016 0.335610568523407 2017 0.331072449684143 2018 0.365629911422729 2019 0.371362656354904 2020 0.398686468601227 2021 0.402841687202454 2022 0.379767835140228