Year Number 1996 0.386360377073288 1998 0.440841853618622 2000 0.416249960660934 2002 0.366997271776199 2003 0.276095181703568 2004 0.319958239793777 2005 0.213636070489883 2006 0.305708646774292 2007 0.366895705461502 2008 0.381994009017944 2009 0.328992426395416 2010 0.352258384227753 2011 0.355162888765335 2012 0.296101152896881 2013 0.290261089801788 2014 0.303565949201584 2015 0.295043766498566 2016 0.319632709026337 2017 0.313955157995224 2018 0.318043142557144 2019 0.31544154882431 2020 0.329134196043015 2021 0.379181206226349 2022 0.324080735445023