Year Number 1996 0.358660489320755 1998 0.392262578010559 2000 0.367690443992615 2002 0.366997271776199 2003 0.276095181703568 2004 0.319958239793777 2005 0.203041076660156 2006 0.266264259815216 2007 0.279377818107605 2008 0.231026411056519 2009 0.216449201107025 2010 0.208097830414772 2011 0.211273431777954 2012 0.230768129229546 2013 0.238375931978226 2014 0.285645455121994 2015 0.274665802717209 2016 0.290534406900406 2017 0.291876524686813 2018 0.30007192492485 2019 0.307287633419037 2020 0.335054785013199 2021 0.325010359287262 2022 0.30890029668808