Year Number 1996 0.387605756521225 1998 0.355241268873215 2000 0.355957746505737 2002 0.316182136535645 2003 0.342772305011749 2004 0.380957245826721 2005 0.373064666986465 2006 0.257984191179276 2007 0.250154078006744 2008 0.245553061366081 2009 0.252307683229446 2010 0.259483873844147 2011 0.258228123188019 2012 0.281423807144165 2013 0.269732594490051 2014 0.268441528081894 2015 0.252808153629303 2016 0.234031811356544 2017 0.24762786924839 2018 0.29508912563324 2019 0.215299054980278 2020 0.226966977119446 2021 0.24368542432785 2022 0.251888811588287